Document:

<PAGE>

                                                                    EXHIBIT 10.5

                                    [LOGO]

Via Federal Express and Facsimile                   TeleCorp PCS, Inc.
---------------------------------                   Suite 800
                                                    1010 N. Glebe Road
February 17, 2001                                   Arlington, VA 22201

Ronald G. Bizcik                                    Tel  703.236.1100
Chief Operating Officer                             Fax  703.236.1101
SBA Towers, Inc.
One Town Center Road, 3rd Floor
Boca Raton, FL 33486

Dear Ron:

        I am writing this letter to confirm our agreement today with respect to
that certain, Purchase Agreement ("Agreement") entered into by and among
TeleCorp Realty, LLC, TeleCorp Puerto Rico Realty, Inc., TeleCorp
Communications, Inc. (collectively "TeleCorp") and SBA Towers, Inc. ("SBA") on
September 15, 2000. SBA and TeleCorp hereby agree that a Closing shall occur on
March 16, 2001, at which time a minimum of two hundred (200) Sites shall be
approved for purchase by SBA and conveyed by TeleCorp to NewCo.

        Subsequent to such Closing and through July 19, 2001, SBA and TeleCorp
shall continue pursuant to Section 7(c) of the Agreement to take Curative
Actions with respect to any Sites subject to the Agreement but not yet closed
upon. One or more Closings upon such sites shall occur at such times or times as
may be agreed upon by the parties. In the event a March 16th 2001 Closing does
not occur as contemplated herein, TeleCorp hereby reserves its right under
Section 7(g) to terminate the Agreement as result of the rejection by SBA of
more than fifteen (15) of the two hundred seventy-five (275) sites which were
subject to the Agreement and to pursue any remedies available to it at law or
equity for breach of the Agreement as modified by this letter agreement.

        Except as set forth herein, all terms and conditions of the Agreement
shall remain in full force and effect. If you agree to the modifications to the
Agreement contained herein, please sign the acknowledgement set forth below and
return the signature page to me via facsimile at (703) 236-1376.

                                                Sincerely,

                                                /s/ Ronald W. Keefe

                                                Ronald W. Keefe, Jr.

Acknowledged and agreed to;
SBA Towers, Inc.

By: /s/ Jeffery A. Stoops
   -----------------------
Its: President
    ----------------------
<PAGE>

cc:
Paul Hines
Gunster Yoakley & Stewart, P.A.
777 South Flagler Drive
Suite 500-East Tower
West Palm Beach, FL 33401

Todd A. Lewellen
Lewellen & Frazier, PLC
415 North McKinley, Suite 1240
Little Rock, AR 72205

John Marino
Jeffery Stoops
SBA Towers, Inc.
One Town Center Road, 3rd Floor
Boca Raton, FL 33486<PAGE>

                                                                     EXHIBIT 4.3

                                                                  EXECUTION COPY
                                                                  --------------

                               TELECORP PCS, INC.

                  Senior Subordinated Discount Notes Due 2011

                         SECURITIES PURCHASE AGREEMENT

                           Dated as of April 3, 2001
<PAGE>

                                TABLE OF CONTENTS

                                                                            Page

1.       Sale; Closings.......................................................2

         1.1      Closings....................................................2
         1.2      Payment.....................................................3
         1.3      Legal Fees..................................................3

2.       Representations, Warranties and Agreements of the Company............3

         2.1      Private Placement...........................................3
         2.2      Organization................................................3
         2.3      Authority...................................................4
         2.4      Legality of Securities Purchase Agreement...................4
         2.5      Legality of Registration Rights Agreement...................4
         2.6      Legality of Indenture.......................................4
         2.7      Legality of Notes...........................................4
         2.8      No Conflict.................................................5
         2.9      SEC Documents; Undisclosed Liabilities......................5
         2.10     Litigation..................................................6
         2.11     Restraints on Issuance......................................6
         2.12     Compliance with Laws and Agreements.........................6
         2.13     Licenses....................................................7
         2.14     Taxes.......................................................7
         2.15     Investment Company; Public Utility Holding Company..........7
         2.16     Management Controls.........................................7
         2.17     Insurance...................................................7
         2.18     Intellectual Property.......................................8
         2.19     Properties..................................................8
         2.20     Labor Matters...............................................8
         2.21     ERISA.......................................................8
         2.22     Environmental...............................................9
         2.23     Business Practices..........................................9
         2.24     Integration.................................................9
         2.25     No General Solicitation.....................................9
         2.26     No Business with Cuba.......................................9
         2.27     No Material Adverse Change..................................9
         2.28     Fee Licenses...............................................10
         2.29     Communications Act.........................................10
         2.30     Build-Out Plan.............................................10
         2.31     Certain Fees...............................................11
         2.32     Margin Securities..........................................11
         2.33     Capitalization.............................................11

3.       Representations of Purchaser........................................11

         3.1      Authority..................................................11

                                      -i-
<PAGE>

         3.2      Legality of Securities Purchase Agreement..................11
         3.3      No Conflict................................................11
         3.4      Securities Act.............................................12

4.       Agreements of the Company...........................................12

         4.1      Reports....................................................12
         4.2      Blue Sky Qualification.....................................12
         4.3      Integration................................................13
         4.4      No General Solicitation....................................13
         4.5      No Offers..................................................13
         4.6      Rule 144...................................................13
         4.7      Investment Company Act.....................................13
         4.8      Availability of Company Personnel..........................14
         4.9      Satisfactory Objections....................................14
         4.10     Net Proceeds...............................................14
         4.11     TeleCorp/Tritel Consent....................................14

5.       Conditions..........................................................14

         5.1      Disclosure; Representations and Warranties.................14
         5.2      Corporate Proceedings......................................14
         5.3      Opinions...................................................15
         5.4      Registration Rights Agreement..............................15
         5.5      Indenture; Notes...........................................15
         5.6      Material Adverse Change....................................15
         5.7      Downgrade of Debt Securities...............................15
         5.8      Procurement Contract.......................................15
         5.9      Consents, Agreements.......................................15
         5.10     No Actions Pending.........................................16
         5.11     Purchase Permitted By Applicable Law.......................16
         5.12     Fees.......................................................16
         5.13     Documentation..............................................16
         5.14     No Events of Default.......................................16

6.       Termination.........................................................16

7.       Special Event of Default............................................16

8.       Definitions.........................................................17

9.       Fees and Expenses...................................................19

10.      Survival of Representations and Warranties..........................20

11.      Amendments and Waivers..............................................20

12.      Notices, etc........................................................20

13.      Indemnification.....................................................21

                                      -ii-
<PAGE>

14.      Successors and Assigns..............................................21

15.      Miscellaneous.......................................................21

16.      Submission To Jurisdiction; Waivers.................................22

17.      WAIVERS OF JURY TRIAL...............................................22

Schedule A     Purchaser Information
Schedule 2.2   Subsidiaries
Schedule 2.18  Intellectual Property
Schedule 2.28  Fee Licenses
Schedule 2.33  Capitalization
Annex A        Form Exchange and Registration Rights Agreement
Exhibit A      Form Purchase Agreement
Exhibit B-1    Form Legal Opinion of Cadwalader, Wickersham & Taft
Exhibit B-2    Form Legal Opinion of Mintz Levin Cohn Ferris Glovsky
                and Popeo, P.C.
Exhibit C      Form Legal Opinion of Wiley, Rein & Fielding
Exhibit D      Form Indenture

                                     -iii-
<PAGE>

TeleCorp PCS, Inc.
1010 North Glebe Road
Arlington, Virginia 22201

                  Senior Subordinated Discount Notes due 2011

                                                                   April 3, 2001

Lucent Technologies Inc.
600 Mountain Avenue
Murray Hill, New Jersey  07974

Ladies and Gentlemen:

          TeleCorp PCS, Inc., a Delaware corporation (the "Company"), has
                                                           -------
authorized and proposes to issue and sell up to $425,000,000 in gross proceeds
of its Senior Subordinated Discount Notes due 2011 (the "Notes").  The Notes
                                                         -----
will be issued pursuant to an Indenture to be dated as of April 6, 2001
substantially in the form attached as Exhibit D hereto (the "Indenture") between
                                      ---------              ---------
the Company and Firstar Bank, N.A., as trustee (the "Trustee") and will be
                                                     -------
guaranteed on an unsecured senior subordinated basis by each of the Subsidiary
Guarantors (as defined in the Indenture), if any; provided that such amount
                                                  --------
shall be reduced dollar for dollar by the principal amount of any notes issued
after the date hereof under the Note Purchase Agreement.

          On or prior to the May 13, 2002, the Company will issue and sell to
you pursuant to the terms of the Indenture and, subject to the terms of this
Agreement, you will purchase from the Company, Notes yielding to the Company up
to $425,000,000 of gross proceeds.

          You and your direct and indirect transferees will be entitled to the
benefits of one or more Exchange and Registration Rights Agreements
substantially in the form attached hereto as Annex A (the "Registration Rights
                                                           -------------------
Agreement") pursuant to which the Company will agree to file with the Securities
---------
and Exchange Commission (the "Commission") (i) a registration statement (the
                              ----------
"Exchange Offer Registration Statement") under the Securities Act of 1933 (the
--------------------------------------
"Securities Act") registering an issue of senior subordinated discount notes of
---------------
the Company (the "Exchange Notes") which are identical in all material respects
                  --------------
to the Notes (except that the Exchange Notes will not contain terms with respect
to transfer restrictions or registration rights) and (ii) under certain
circumstances, a shelf registration statement under the Securities Act (the
"Shelf Registration Statement").
-----------------------------

          Certain capitalized terms used in this Agreement are defined in

Section 8; all references to a "Schedule" or an "Exhibit" are, unless otherwise
---------
specified, to a Schedule or an Exhibit attached to this Agreement.
<PAGE>

     The Company hereby agrees with you as follows:

     1. Sale; Closings.
        ---------------

     1.1 Closings. (a) The following sales of Notes to be purchased by you shall
         --------
take place (each a "Closing") as follows: (i) on the Initial Closing Date (the
                    -------
"April Closing") you shall purchase the Company's senior subordinated discount
 -------------
notes with a yield of 11.0%, yielding to the Company gross proceeds of
$100,000,000 (the "April Notes"), (ii) on the October Closing Date, you shall
                   -----------
purchase the Company's senior subordinated discount notes with a yield of 11.0%,
yielding to the Company gross proceeds of $100,000,000 (the "October Notes") and
                                                             -------------
(iii) after the October Closing Date, at any time and from time to time upon at
least five (5) Business Days' notice given by the Company specifying the amount
of Market Notes to be purchased and the purchase date (each a "Market Note
                                                               -----------
Notice"), you shall purchase the Company's senior subordinated discount notes
------
(the "Market Notes"), and together with the April Notes and the October Notes,
      ------------
the "Notes") with a yield equal to the lesser of (x) 12% and (y) 25 basis points
     -----
below the average of the closing sale yield for the TeleCorp Wireless, Inc.
senior subordinated discount notes due 2009 (the "Wireless Notes") as quoted by
                                                  --------------
three (3) market makers of the Wireless Notes, chosen in good faith by the
Company and you on or before September 15, 2001, over the five (5) trading days
prior to the delivery of the Market Note Notice, yielding to the Company gross
proceeds of an aggregate of $225,000,000 (the "Market Note Facility"). Each
                                               --------------------
closing shall occur on the applicable Closing Date or such other time as the
Company and you may agree and at such location as the Company and you may agree.

     (b) The Company may make multiple draws on the Market Note Facility;
provided, that (i) each draw shall be in an amount yielding to the Company gross
--------
proceeds of at least $50,000,000 and (ii) the Company shall not make more than
three (3) draws in the aggregate. The Market Note Facility shall terminate on
May 13, 2002.

     (c) The April Closing shall be subject to the satisfaction on the Initial
Closing Date of each of the conditions set forth in Section 5. If within five
                                                    ---------
(5) business days after the Initial Closing Date you enter into a secondary
sales agreement substantially similar to the form attached hereto as Exhibit A
                                                                     ---------
with one or more secondary purchasers, the Company will enter into a further
agreement with you giving you, upon the closing of the transaction provided for
in the secondary sales agreement, the benefits of the representations,
warranties and indemnification contained in such agreement. In connection with
the transactions described in the preceding sentence, if requested by any
secondary purchaser, at the closing of such transactions, the Company,
concurrent with receipt of a termination of the Registration Rights Agreement
with you, will enter into a substantially similar agreement with such secondary
purchasers. All Closings subsequent to the April Closing shall be subject solely
to the satisfaction of the conditions contained in Sections 5.1, 5.4, 5.5, 5.8,
                                                   ------------  ---  ---  ---
5.9(b), 5.11(a) and 5.14 (collectively the "Subsequent Conditions"); provided,
------  -------     ----                    ---------------------    --------
that if you deliver written notice to the Company that you will be entering into
a concurrent sale of the October Notes or the Market Notes, as applicable, with
one or more secondary purchasers (such notice to be delivered not less than ten
(10) business days prior to the October Closing and within two (2) business days
of any Market Note Notice) the Company (i) shall use its good faith efforts to
enter into a purchase agreement with such secondary purchasers which the Company
reasonably believes has customary terms and conditions and, in respect of any
such sale, shall enter into a supplemental agreement with you

                                      -2-
<PAGE>

which the Company reasonably believes corresponds to the purchase agreement with
such secondary purchasers (it being understood that, (x) the Company's failure
to enter into an agreement, either with such secondary purchasers or you, shall
not relieve you of your obligations to purchase Notes hereunder and (y) if such
agreements are entered into and the secondary sales contemplated by such
agreements are not consummated, such agreements shall be terminated and the
October Closing or Market Closing, as applicable, shall be subject only to the
satisfaction on the applicable Closing Date of each of the Subsequent
Conditions) and (ii) solely in respect of any Market Note Closing Date, will
extend such Closing Date by up to five (5) business days or such further
additional time as may be necessary to accommodate such secondary sale; provided
                                                                        --------
that in no event will the Company be required to extend such Closing Date by
more than ten (10) business days in the aggregate.

     (d) At each Closing, the Company will deliver to you the Notes to be
purchased by you in the form of a single Note (or such greater number of Notes
in denominations of at least $1,000 as you may reasonably request in a notice to
the Company not less than two (2) Business Days prior to the applicable Closing
Date) dated the applicable Closing Date and registered in your name (or in the
name of your nominee).

     (e) Each issuance of Notes shall be pursuant to the Indenture and the
parties shall have entered into one or more registration rights agreements each
of which is substantially identical to the Registration Rights Agreement.

     1.2 Payment. Payment for each of the Notes shall be in immediately
         -------
available funds.

     1.3 Legal Fees. On the Closing Date, the Company will pay the reasonable
         ----------
fees and disbursements of your special counsel in connection with the
transactions contemplated by this Agreement and thereafter the Company will
promptly pay additional reasonable fees and disbursements of such special
counsel incurred in connection with such transactions.

     2. Representations, Warranties and Agreements of the Company. The Company
        ---------------------------------------------------------
represents and warrants to, and agrees with you as follows (provided that the
                                                            --------
Transactional Representations shall be qualified by disclosure in the Company's
SEC Documents):

     2.1 Private Placement. Assuming the accuracy of your representations and
         -----------------
warranties contained in Section 3 and your compliance with the agreements set
                        ---------
forth therein, it is not necessary, in connection with the issuance and sale of
the Notes to you and the offer, resale and delivery of the Notes by you in the
manner contemplated by this Agreement to register the Securities under the
Securities Act or to qualify the Indenture under the Trust Indenture Act of 1939
(the "Trust Indenture Act").
      -------------------

     2.2 Organization. Except as set forth in Schedule 2.2 hereto, the Company
         ------------                         ------------
has no subsidiaries and holds no minority interest in any entity. The Company
and each of its subsidiaries have been duly incorporated or formed and are
validly existing as corporations, limited liability companies or limited
partnerships in good standing under the laws of their respective jurisdictions
of incorporation or formation, are duly qualified to do business and are in good
standing as foreign corporations, limited liability companies or limited
partnerships in each

                                      -3-
<PAGE>

jurisdiction in which their respective ownership or lease of property or the
conduct of their respective businesses requires such qualification, and have all
power and authority necessary to own or hold their respective properties and to
conduct the businesses in which they are engaged, except where the failure to so
qualify or have such power or authority could not, singularly or in the
aggregate, be reasonably expected to have a material adverse effect on (i) the
condition (financial or otherwise), results of operations, business or business
prospects of the Company and its subsidiaries taken as a whole, (ii) the ability
of the Company or any of its subsidiaries to perform its obligations under the
Transaction Documents or (iii) the validity or enforceability of any Transaction
Document or the rights and remedies of the Holders of the Notes (a "Material
                                                                    --------
Adverse Effect").
--------------

     2.3 Authority. The Company has full right, power and authority to execute
         ---------
and deliver this Agreement, the Indenture, the Registration Rights Agreement and
the Notes (collectively, the "Transaction Documents") and to perform its
                              ---------------------
obligations hereunder and thereunder; and all corporate action required to be
taken for the due and proper authorization, execution and delivery of each of
the Transaction Documents and the consummation of the transactions contemplated
thereby have been duly and validly taken.

     2.4 Legality of Securities Purchase Agreement. This Agreement has been duly
         -----------------------------------------
authorized, executed and delivered by the Company and constitutes a valid and
legally binding agreement of the Company.

     2.5 Legality of Registration Rights Agreement. The Registration Rights
         -----------------------------------------
Agreement has been duly authorized by the Company and, when duly executed and
delivered in accordance with its terms by each of the parties thereto, will
constitute a valid and legally binding agreement of the Company enforceable
against the Company in accordance with its terms, except to the extent that such
enforceability may be limited by applicable bankruptcy, insolvency, fraudulent
conveyance, reorganization, moratorium and other similar laws affecting
creditors rights generally and by general equitable principles (whether
considered in a proceeding in equity or at law).

     2.6 Legality of Indenture. The Indenture has been duly authorized by the
         ---------------------
Company and, when duly executed and delivered in accordance with its terms by
each of the parties thereto, will constitute a valid and legally binding
agreement of the Company enforceable against the Company in accordance with its
terms, except to the extent that such enforceability may be limited by
applicable bankruptcy, insolvency, fraudulent conveyance, reorganization,
moratorium and other similar laws affecting creditors rights generally and by
general equitable principles (whether considered in a proceeding in equity or at
law). On the Closing Date, the Indenture will conform in all material respects
to the requirements of the Trust Indenture Act and the rules and regulations of
the Commission applicable to an indenture which is qualified thereunder.

     2.7 Legality of Notes. The Notes have been duly authorized by the Company
         -----------------
and, when duly executed, authenticated, issued and delivered as provided in the
Indenture and paid for as provided herein, will be duly and validly issued and
outstanding and will constitute valid and legally binding obligations of the
Company, as issuer, entitled to the benefits of the Indenture and enforceable
against the Company as issuer, in accordance with their terms, except

                                      -4-
<PAGE>

to the extent that such enforceability may be limited by applicable bankruptcy,
insolvency, fraudulent conveyance, reorganization, moratorium and other similar
laws affecting creditors rights generally and by general equitable principles
(whether considered in a proceeding in equity or at law).

     2.8 No Conflict. The execution, delivery and performance by the Company of
         -----------
each of the Transaction Documents to which it is a party, the issuance,
authentication, sale and delivery of the Notes and compliance by the Company
with the terms thereof and the consummation of the transactions contemplated by
the Transaction Documents (a) will not conflict with or result in a breach or
violation of any of the terms or provisions of, or constitute a default under,
or result in the creation or imposition of any lien, charge or encumbrance upon
any property or assets of the Company or any of its subsidiaries (other than as
provided by the Indenture) pursuant to, any material indenture, mortgage, deed
of trust, loan agreement or other material agreement or instrument to which the
Company or any of its subsidiaries is a party or by which the Company or any of
its subsidiaries is bound or to which any of the property or assets of the
Company or any of its subsidiaries is subject, nor will such actions result in
any violation of the provisions of the charter or by-laws of the Company or any
of its subsidiaries or any statute or any judgment, order, decree, rule or
regulation of any court or arbitrator or governmental agency or body having
jurisdiction over the Company or any of its subsidiaries or any of their
properties or assets; except where such conflict, breach, violation, default or
lien, charge or encumbrance would not, singularly or in the aggregate, have a
Material Adverse Effect and (b) no consent, approval, authorization or order of,
or filing or registration with, any such court or arbitrator or governmental
agency or body under any such statute, judgment, order, decree, rule or
regulation is required for the execution, delivery and performance by the
Company of each of the Transaction Documents, the issuance, authentication, sale
and delivery of the Notes and compliance by the Company with the terms thereof
and the consummation of the transactions contemplated by the Transaction
Documents, except for such consents, approvals, authorizations, filings,
registrations or qualifications (i) which shall have been obtained or made prior
to the Closing Date, (ii) as may be required to be obtained or made under the
Securities Act and the rules and regulations promulgated thereunder and
applicable state securities laws as provided in the Registration Rights
Agreement, (iii) which the failure to obtain could not reasonably be expected to
have a Material Adverse Effect or (iv) which are otherwise not material in the
context of the sale of the Notes.

     2.9 SEC Documents; Undisclosed Liabilities. Since March 30, 2000, the
         --------------------------------------
Company and its subsidiaries have filed with the Commission all reports,
schedules, forms, statements and other documents (including exhibits and all
other information incorporated therein, the "SEC Documents") required to be
                                             -------------
filed under the Securities Act and the Securities Exchange Act of 1934 (the
"Exchange Act"). As of their respective dates, the SEC Documents complied in all
 ------------
material respects with the requirements of the Securities Act or the Exchange
Act, as the case may be, and the rules and regulations of the SEC promulgated
thereunder applicable to such SEC Documents. Except to the extent that
information contained in any SEC Document has been revised or superseded by a
later filed SEC Document, none of the SEC Documents when filed contained any
untrue statement of a material fact or omitted to state a material fact required
to be stated therein or necessary in order to make the statements therein, in
light of the circumstances under which they were made, not misleading. The
financial statements of the Company and its subsidiaries included in the SEC
Documents comply as to

                                      -5-
<PAGE>

form, as of their respective dates of filing with the SEC, in all material
respects with applicable accounting requirements and the published rules and
regulations of the Commission with respect thereto, have been prepared in
accordance with generally accepted accounting principles (except, in the case of
unaudited statements, as permitted by Form 10-Q of the Commission) applied on a
consistent basis during the periods involved (except as may be indicated in the
notes thereto) and fairly present in all material respects the consolidated
financial position of the Company and its subsidiaries as of the dates thereof
and the results of their operations and cash flows for the periods then ended
(subject, in the case of unaudited statements, to normal recurring year-end
audit adjustments). Except for liabilities (i) reflected in such financial
statements or in the notes thereto, (ii) incurred in the ordinary course of
business consistent with past practice since the date of the most recent audited
financial statements included in the SEC Documents, or (iii) incurred in
connection with this Agreement or the transactions contemplated hereby, neither
the Company nor any of its subsidiaries has any liabilities or obligations
(whether absolute, accrued, contingent or otherwise) of any nature which,
individually or in the aggregate, could reasonably be expected to have a
Material Adverse Effect on the Company or its subsidiaries taken as a whole.

     2.10 Litigation. There are no legal or governmental proceedings pending to
          ----------
which the Company or any of its subsidiaries is a party or of which any property
or assets of the Company or any of its subsidiaries is the subject, other than
proceedings described in the SEC Documents affecting the wireless communications
industry generally which (i) singularly or in the aggregate, if determined
adversely to the Company or any of its subsidiaries, could reasonably be
expected to have a Material Adverse Effect or (ii) question the validity or
enforceability of any of the Transaction Documents or any action taken or to be
taken pursuant thereto; and to the best knowledge of the Company, no such
proceedings are threatened or contemplated by governmental authorities or
threatened by others.

     2.11 Restraints on Issuance. (a) To the best knowledge of the Company, no
          -----------------------
action has been taken and no statute, rule, regulation or order has been
enacted, adopted or issued by any governmental agency or body which prevents the
issuance of the Notes or suspends the sale of the Notes in any jurisdiction; (b)
no injunction, restraining order or order of any nature by any federal or state
court of competent jurisdiction has been issued with respect to the Company or
any of its subsidiaries which would prevent or suspend the issuance or sale of
the Notes in any jurisdiction; (c) no action, suit or proceeding is pending
against or, to the best knowledge of the Company, threatened against or
affecting the Company or any of its subsidiaries before any court or arbitrator
or any governmental agency, body or official, domestic or foreign, which could
reasonably be expected to interfere with or adversely affect the issuance of the
Notes or in any manner draw into question the validity or enforceability of any
of the Transaction Documents or any action taken or to be taken pursuant
thereto.

     2.12 Compliance with Laws and Agreements. Neither the Company nor any of
          ------------------------------------
its subsidiaries is (i) in violation of its charter, by-laws, operating
agreement or limited partnership agreement, as appropriate, (ii) in default, and
no event has occurred which, with notice or lapse of time or both, would
constitute a default, in the due performance or observance of any term, covenant
or condition contained in any material indenture, mortgage, deed of trust, loan
agreement or other material agreement or instrument to which it is a party or by
which it is bound or to which any of its property or assets is subject or (iii)
in violation of any law,

                                      -6-
<PAGE>

ordinance, governmental rule, regulation or court decree to which it or its
property or assets may be subject, except, in the case of clause (ii) or clause
(iii), for any default or violation that could not reasonably be expected to
have a Material Adverse Effect.

     2.13 Licenses. Except as disclosed in the SEC Documents, the Company and
          --------
each of its subsidiaries possess all material licenses, certificates,
authorizations and permits issued by, and have made all declarations and filings
with, the appropriate federal, state or foreign regulatory agencies or bodies
which are necessary or desirable for the ownership of their respective
properties or the conduct of their respective businesses, except where the
failure to possess or make the same would not, singularly or in the aggregate,
have a Material Adverse Effect, and neither the Company nor any of its
subsidiaries has received notification of any revocation or modification of any
such license, certificate, authorization or permit or has any reason to believe
that any such license, certificate, authorization or permit will not be renewed
in the ordinary course.

     2.14 Taxes. The Company and each of its subsidiaries have filed all
          -----
federal, state, local and foreign income and franchise tax returns required to
be filed through the date hereof and have paid all taxes due thereon, and no tax
deficiency has been determined adversely to the Company or any of its
subsidiaries which has had (nor does the Company or any of its subsidiaries have
any knowledge of any tax deficiency which, if determined adversely to the
Company or any of its subsidiaries, could reasonably be expected to have) a
Material Adverse Effect.

     2.15 Investment Company; Public Utility Holding Company. Neither the
          ---------------------------------------------------
Company nor any of its subsidiaries is (i) an investment company or a company
controlled by an investment company within the meaning of the Investment Company
Act of 1940, as amended (the Investment Company Act), and the rules and
regulations of the Commission thereunder or (ii) a holding company or a
subsidiary company of a holding company or an affiliate thereof within the
meaning of the Public Utility Holding Company Act of 1935, as amended.

     2.16 Management Controls. The Company and each of its subsidiaries maintain
          -------------------
a system of internal accounting controls sufficient to provide reasonable
assurance that (i) transactions are executed in accordance with management's
general or specific authorizations; (ii) transactions are recorded as necessary
to permit preparation of financial statements in conformity with generally
accepted accounting principles and to maintain asset accountability; (iii)
access to financial assets is permitted only in accordance with management's
general or specific authorization; and (iv) the recorded accountability for
assets is compared with the existing assets at reasonable intervals and
appropriate action is taken with respect to any differences to the extent
necessary.

     2.17 Insurance. The Company and each of its subsidiaries have insurance
          ---------
covering their respective properties, operations, personnel and businesses,
which insurance is in amounts and insures against such losses and risks as are
adequate to protect the Company and its subsidiaries and their respective
businesses, determined by reference to the insurance maintained by other
companies in the wireless communications industry. Neither the Company nor any
of its subsidiaries has received notice from any insurer or agent of such
insurer that capital

                                      -7-
<PAGE>

improvements or other expenditures are required or necessary to be made in order
to continue such insurance.

     2.18 Intellectual Property. Except as disclosed in Schedule 2.18, the
          ---------------------                         --------------
Company and each of its subsidiaries own or possess adequate rights to use all
patents, patent applications, trademarks, service marks, trade names, trademark
registrations, service mark registrations, copyrights, licenses and know-how
(including trade secrets and other unpatented and/or unpatentable proprietary or
confidential information, systems or procedures) necessary for the conduct of
their respective businesses, except where the failure to possess such rights
could not reasonably be expected to have a Material Adverse Effect; and the
conduct of their respective businesses will not conflict in any respect with,
and the Company and its subsidiaries have not received any notice of any claim
of conflict with, any such rights of others that, if determined adversely to the
Company or any of its subsidiaries would, individually or in the aggregate, have
a Material Adverse Effect.

     2.19 Properties. The Company and each of its subsidiaries have good and
          ----------
marketable title in fee simple to, or have valid rights to lease or otherwise
use, all items of real and personal property which are material to the business
of the Company and its subsidiaries, in each case free and clear of all liens,
encumbrances, claims and defects and imperfections of title except such as (i)
do not materially interfere with the use made and proposed to be made of such
property by the Company and its subsidiaries or (ii) could not reasonably be
expected to have a Material Adverse Effect.

     2.20 Labor Matters. No labor disturbance by or dispute with the employees
          -------------
of the Company or any of its subsidiaries exists or, to the best knowledge of
the Company, is contemplated or threatened.

     2.21 ERISA. No prohibited transaction (as defined in Section 406 of the
          -----
Employee Retirement Income Security Act of 1974, as amended, including the
regulations and published interpretations thereunder ("ERISA"), or Section 4975
                                                       -----
of the Internal Revenue Code of 1986, as amended from time to time (the "Code"))
                                                                         ----
or accumulated funding deficiency (as defined in Section 302 of ERISA) or any of
the events set forth in Section 4043(b) of ERISA (other than events with respect
to which the 30-day notice requirement under Section 4043 of ERISA has been
waived) has occurred with respect to any employee benefit plan of the Company or
any of its subsidiaries which could reasonably be expected to have a Material
Adverse Effect; each such employee benefit plan is in compliance in all material
respects with applicable law, including ERISA and the Code, except where such
noncompliance, individually or in the aggregate, could not reasonably be
expected to have a Material Adverse Effect; the Company and each of its
subsidiaries have not incurred and do not expect to incur liability under Title
IV of ERISA with respect to the termination of, or withdrawal from, any pension
plan for which the Company or any of its subsidiaries would have any liability;
and each such pension plan that is intended to be qualified under Section 401(a)
of the Code has filed for or received a favorable determination letter from the
Internal Revenue Service and the Company has not amended any such pension plan
in any way that could reasonably be expected to cause the loss of such
qualification.

                                      -8-
<PAGE>

     2.22 Environmental. There has been no storage, generation, transportation,
          -------------
handling, treatment, disposal, discharge, emission or other release of any kind
of toxic or other wastes or other hazardous substances by, due to or caused by
the Company or any of its subsidiaries (or, to the best knowledge of the
Company, any other entity (including any predecessor) for whose acts or
omissions the Company or any of its subsidiaries is or could reasonably be
expected to be liable) upon any of the property now or previously owned or
leased by the Company or any of its subsidiaries, or upon any other property, in
violation of any statute or any ordinance, rule, regulation, order, judgment,
decree or permit or which would, under any statute or any ordinance, rule
(including rule of common law), regulation, order, judgment, decree or permit,
give rise to any liability, except for any violation or liability that could not
reasonably be expected to have, singularly or in the aggregate with all such
violations and liabilities, a Material Adverse Effect; and there has been no
disposal, discharge, emission or other release of any kind onto such property or
into the environment surrounding such property of any toxic or other wastes or
other hazardous substances with respect to which the Company has knowledge,
except for any such disposal, discharge, emission or other release of any kind
which could not reasonably be expected to have, singularly or in the aggregate
with all such discharges and other releases, a Material Adverse Effect.

     2.23 Business Practices. Neither the Company nor, to the best knowledge of
          ------------------
the Company, any director, officer, agent, employee or other person associated
with or acting on behalf of the Company or any of its subsidiaries has (i) used
any corporate funds for any unlawful contribution, gift, entertainment or other
unlawful expense relating to political activity; (ii) made any direct or
indirect unlawful payment to any foreign or domestic government official or
employee from corporate funds; (iii) violated or is in violation of any
provision of the Foreign Corrupt Practices Act of 1977, as amended; or (iv) made
any unlawful bribe, rebate, payoff, influence payment, kickback or other
unlawful payment.

     2.24 Integration. Neither the Company nor any of its affiliates has,
          -----------
directly or through any agent, sold, offered for sale, solicited offers to buy
or otherwise negotiated in respect of, any security (as such term is defined in
the Securities Act), which is or will be integrated with the sale of the Notes
in a manner that would require registration of the Securities under the
Securities Act.

     2.25 No General Solicitation. None of the Company or any of its affiliates
          -----------------------
or any other person acting on its or their behalf has engaged, in connection
with the offering of the Notes, in any form of general solicitation or general
advertising within the meaning of Rule 502(c) under the Securities Act.

     2.26 No Business with Cuba. None of the Company or any of its subsidiaries
          ---------------------
does business with the government of Cuba or with any person or affiliate
located in Cuba within the meaning of Florida Statutes Section 517.075.

     2.27 No Material Adverse Change. Since July 10, 2000, (i) there has been no
          --------------------------
material adverse change or any development involving a prospective material
adverse change in the condition, financial or otherwise, or in the earnings,
business affairs, management or business prospects of the Company and its
subsidiaries, taken as a whole, whether or not arising in the ordinary course of
business, (ii) the Company has not incurred any material liability or

                                      -9-
<PAGE>

obligation, direct or contingent, other than in the ordinary course of business,
(iii) the Company has not entered into any material transaction other than in
the ordinary course of business and (iv) there has not been any change in the
capital stock or long-term debt of the Company, or any dividend or distribution
of any kind declared, paid or made by the Company on any class of its capital
stock.

     2.28 Fee Licenses. (i) The Company and its subsidiaries have the full use
          ------------
and benefit of all broadband personal communications services ("PCS") licenses
                                                                ---
issued by the Federal Communications Commission (the "FCC") to the Company and
                                                      ---
its subsidiaries (the "Licenses") necessary to operate assets constituting a
radio communications system authorized under the rules for wireless
communications services (including any license and the network, marketing,
distribution, sales, customer interface and operations functions relating
thereto) owned and operated by the Company or any of its subsidiaries in the
Major Trading Areas (as defined in 47 C.F.R. 24.202) and the Basic Trading Areas
(as defined in 47 C.F.R. 24.202) listed on Parts A, B, C and D of Schedule 2.28
                                                                  -------------
and each other area in which the Company or any of its subsidiaries conducts a
broadband PCS business; (ii) such Licenses have been duly issued by the FCC, are
(in the case of Licenses listed on Parts A, B, C and D of Schedule 2.28) or will
                                                          -------------
be (upon consummation of the relevant transaction in the case of Licenses listed
on Parts E and F of Schedule 2.28) held by a wholly owned subsidiary of the
                    -------------
Company and are in full force and effect and (iii) the Company and its
subsidiaries are in compliance in all material respects with all the provisions
of each such License held by any of them.

     2.29 Communications Act. (i) The Company and each of its subsidiaries are
          ------------------
in compliance in all material respects with the Communications Act of 1934, and
                                                ------------------
any similar or successor federal statute, and the rules and regulations and
published policies of the FCC thereunder, as amended and as in effect from time
to time (collectively, the "Communications Act"), and all requirements of the
FCC, including the rules for holding very small business licenses (as defined in
47 C.F.R. 24.720 and 24.839); (ii) the Company has no knowledge of any
investigation, notice of apparent liability, violation, forfeiture or other
order or complaint issued by or before the FCC, or of any other proceedings
(other than proceedings relating to the wireless communications industries
generally) of or before the FCC, which could reasonably be expected to have a
Material Adverse Effect; (iii) no event has occurred which (A) has resulted in,
or after notice or lapse of time or both would result in, revocation,
suspension, adverse modifications, non-renewal, impairment, restriction or
termination of, or order of forfeiture with respect to, any License in any
respect which could reasonably be expected to have a Material Adverse Effect or
(B) affects or could reasonably be expected in the future to affect any of the
rights of the Company or any of its subsidiaries under any License held by the
Company or any of its subsidiaries in any respect which could reasonably be
expected to have a Material Adverse Effect; (iv) the Company and each of its
subsidiaries have duly filed in a timely manner all material filings, reports,
applications, documents, instruments and information required to be filed under
the Communications Act, and all such filings were when made true, correct and
complete in all material respects; and (v) the Company has no reason to believe
that each License of the Company or any of its subsidiaries will not be renewed
in the ordinary course.

     2.30 Build-Out Plan. TeleCorp Wireless is in compliance in all material
          --------------
respects with its Minimum Build-Out Plan, as defined in the Securities Purchase
Agreement dated January 23, 1998, among AT&T Wireless PCS Inc., TWR Cellular,
Inc., the Cash Equity

                                      -10-
<PAGE>

Investors (as identified therein), the TeleCorp Investors (as identified
therein), Gerald Vento, Thomas Sullivan and TeleCorp Wireless (the "Equity
                                                                    ------
Securities Purchase Agreement").
------------------------------

     2.31 Certain Fees. No broker's or finder's fee or commission has been paid
          ------------
or will be payable by the Company with respect to the offer, issue and sale of
the Notes or with respect to the transactions contemplated hereunder and the
Company hereby indemnifies you against, and will hold you harmless from, any
claim, demand or liability asserted against you for broker's or finder's fees
alleged to have been incurred by the Company or any other Person (other than you
or your affiliates) in connection with any such offer, issue and sale or the
transactions contemplated hereunder or any of the other transactions
contemplated by this Agreement.

     2.32 Margin Securities. None of the proceeds of the sale of the Securities
          -----------------
will be used, directly or indirectly, for the purpose of purchasing or carrying
any margin security as that term is defined in Regulation U of the Board of
Governors of the Federal Reserve System (the "Federal Reserve Board"), for the
purpose of reducing or retiring any indebtedness which was originally incurred
to purchase or carry any margin security or for any other purpose which might
cause any of the Notes to be considered a purpose credit within the meanings of
Regulation T, U or X of the Federal Reserve Board.

     2.33 Capitalization. As of the Closing Date, the Company will have an
          --------------
authorized capitalization as set forth in the SEC Documents; all the outstanding
shares of capital stock of the Company have been duly and validly authorized and
issued and are fully paid and non-assessable; and the capital stock of the
Company conforms in all material respects to the description thereof contained
in the SEC Documents. All the outstanding shares of capital stock of each
subsidiary of the Company have been duly and validly authorized and issued, are
fully paid and non-assessable and, except as set forth on Schedule 2.33, are
                                                          -------------
owned directly or indirectly by the Company, free and clear of any Lien.

     3. Representations of Purchaser. You represent, warrant and agree that
        ----------------------------

     3.1 Authority. You have the full right, power and authority to execute and
         ---------
deliver this Agreement and to perform your obligations hereunder; and all
corporate action required to be taken for the due and proper authorization,
execution and delivery of this Agreement and the consummation of the
transactions contemplated hereby have been duly and validly taken.

     3.2 Legality of Securities Purchase Agreement. This Agreement has been duly
         ------------------------------------------
authorized, executed and delivered by you and constitutes your valid and legally
binding agreement.

     3.3 No Conflict. The execution, delivery and performance by you of this
         -----------
Agreement and compliance by you with the terms hereof and the consummation of
the transactions contemplated hereby:

     (a) will not conflict with or result in a breach or violation of any of the
terms or provisions of, or constitute a default under, or result in the creation
or imposition of any lien, charge or encumbrance upon any of your property or
assets pursuant to any material indenture,

                                      -11-
<PAGE>

mortgage, deed of trust, loan agreement or other material agreement or
instrument to which you are party or by which you are bound or to which any of
your property or assets is subject, nor will such actions result in any
violation of the provisions of your charter or by-laws or any statute or any
judgment, order, decree, rule or regulation of any court or arbitrator or
governmental agency or body having jurisdiction over you or any of your
properties or assets; except where such conflict, breach, violation, default or
                      ------
lien, charge or encumbrance could not reasonably be expected to have, singularly
or in the aggregate, a material adverse effect on (i) your condition (financial
or otherwise), results of operations, business or business prospects, (ii) your
ability to perform your obligation under this Agreement or (iii) the validity or
enforceability of this Agreement;

     (b) no consent, approval, authorization or order of, or filing or
registration with, any such court or arbitrator or governmental agency or body
under any such statute, judgment, order, decree, rule or regulation is required
for the execution, delivery and performance by you of this Agreement and
compliance by you with the terms hereof and the consummation of the transactions
contemplated hereby, except for such consents, approvals, authorizations,
filings, registrations or qualifications (i) which shall have been obtained or
made prior to the Closing Date, (ii) as may be required to be obtained or made
under the Securities Act and the rules and regulations promulgated thereunder
and applicable state securities laws as provided in the Registration Rights
Agreement, (iii) the failure to obtain could not reasonably be expected to have
a material adverse effect (as set forth in clauses (i), (ii) and (iii) of
paragraph (a) above) or (iv) which are otherwise not material in the context of
the purchase of the Notes.

     3.4 Securities Act. (a) You are purchasing the Notes pursuant to a private
         ---------------
sale exempt from registration under the Securities Act and (b) you have not
solicited offers for, or offered or sold, and will not solicit offers for, or
offer or sell, the Securities by means of any form of general solicitation or
general advertising within the meaning of Rule 502(c) of Regulation D under the
Securities Act ("Regulation D") or in any manner involving a public offering
within the meaning of Section 4(2) of the Securities Act.

     4. Agreements of the Company. The Company agrees:
        -------------------------

     4.1 Reports. For so long as the Notes are outstanding, to furnish to you
         -------
copies of any annual reports, quarterly reports and current reports filed by the
Company with the Commission on Forms 10-K, 10-Q and 8-K, or such other similar
forms as may be designated by the Commission, and such other documents, reports
and information as shall be furnished by the Company to the Trustee or to the
Holders of the Notes pursuant to the Indenture or the Exchange Act or any rule
or regulation of the Commission thereunder.

     4.2 Blue Sky Qualification. The Company shall promptly take from time to
         -----------------------
time such actions as you may reasonably request to qualify the Notes for
offering and sale under the securities or blue sky laws of such jurisdictions as
you may designate and to continue such qualifications in effect for so long as
required for the resale of the Notes; and to arrange for the determination of
the eligibility for investment of the Notes under the laws of such jurisdictions
as you may reasonably request; provided that the Company and its subsidiaries
shall not be obligated to qualify as foreign corporations in any jurisdiction in
which they are not so qualified or to file a general consent to service of
process in any jurisdiction.

                                      -12-
<PAGE>

     4.3 Integration. The Company shall not, and the Company shall cause its
         -----------
affiliates not to, sell, offer for sale or solicit offers to buy or otherwise
negotiate in respect of any security (as such term is defined in the Securities
Act) which could be integrated with the sale of the Securities in a manner which
would require registration of the Securities under the Securities Act.

     4.4  No General Solicitation.  Except following the effectiveness of the
          -----------------------
Exchange Offer Registration Statement or the Shelf Registration Statement, as
the case may be, the Company shall not, shall cause its affiliates not to, and
shall not authorize or knowingly permit any person acting on its behalf to,
solicit any offer to buy or offer to sell the Securities by means of any form of
general solicitation or general advertising within the meaning of Regulation D
or in any manner involving a public offering within the meaning of Section 4(2)
of the Securities Act; and not to offer, sell, contract to sell or otherwise
dispose of, directly or indirectly, any securities under circumstances where
such offer, sale, contract or disposition would cause the exemption afforded by
Section 4(2) of the Securities Act to cease to be applicable to the offering and
sale of the Notes.

     4.5  No Offers.  For a period of 180 days from the Initial Closing Date,
          ---------
the Company shall not offer for sale, sell, contract to sell, pledge or
otherwise dispose of, directly or indirectly, or file a registration statement
for, or announce any offer, sale, contract for sale of or other disposition of
any debt securities issued or guaranteed by the Company or any of its
subsidiaries (other than (i) the Notes or the Exchange Securities, (ii) notes
issued by the Company pursuant to the Note Purchase Agreement (iii) debt
securities issued or guaranteed by the Company or any of its subsidiaries
pursuant to credit arrangements with a vendor or supplier or any financial
institution acting on behalf of such vendor or supplier; provided that any such
vendor credit arrangement contains terms prohibiting the remarketing of all debt
securities issued or guaranteed thereunder for a period of not less than 180
days from the Closing Date, (iv) the 11 5/8% Senior Subordinated Discount Notes
issued by TeleCorp Wireless pursuant to an Indenture dated April 23, 1999 and
the Telecorp Wireless Notes, (v) the Tritel 2011 Notes and (vi) any debt
securities issued by the Company or any of its subsidiaries to the U.S.
Government in connection with the acquisition of any License from the FCC or any
debt securities assumed by the Company or any of its subsidiaries in connection
with the acquisition of any License or any entity engaged in a Permitted
Business (as defined in the Indenture).

     4.6  Rule 144.  During the period from the Closing Date until two years
after the Closing Date, without your prior written consent, the Company will
not, and will not permit any of its affiliates (as defined in Rule 144 under the
Securities Act) to, resell any of the Notes that have been reacquired by them,
except for Notes purchased by the Company or any of its affiliates and resold in
a transaction registered under the Securities Act.

     4.7  Investment Company Act.  For two years following the date on which the
          ----------------------
Notes are issued, the Company will not be or become, or be or become owned by,
an open-end investment company, unit investment trust or face-amount certificate
company that is or is required to be registered under Section 8 of the
Investment Company Act, and to not be or become, or be or become owned by, a
closed-end investment company required to be registered, but not registered
thereunder.

                                      -13-
<PAGE>

     4.8  Availability of Company Personnel.  In connection with the offering of
          ---------------------------------
the Notes, the Company will make its officers, employees, independent
accountants and legal counsel reasonably available upon request by you.
Notwithstanding anything to the contrary contained herein, no Company officer,
director, employee or other representative shall be required to go on a road
show related to the sale of the Notes by you or any selling agent or agents or
underwriter or underwriters.

     4.9  Satisfactory Objections.  The Company shall do and perform all things
          -----------------------
required to be done and performed by it under this Agreement that are within its
control prior to or after the Closing Date, and shall use commercially
reasonable efforts to satisfy all conditions precedent on its part to the
delivery of the Notes.

     4.10  Net Proceeds.  The Company shall apply the net proceeds from the sale
           ------------
of the Notes for general corporate purposes.

     4.11  TeleCorp/Tritel Consent.  To the extent not previously obtained, the
           -----------------------
Company shall use its reasonable best efforts to obtain under the Tritel Credit
Agreement or the TeleCorp Wireless Credit Agreement, as applicable, the consent
contemplated under the definition of  the "TeleCorp/Tritel Consent" .

     5.  Conditions.  Your obligation to purchase the Notes hereunder is subject
         -----------
to the accuracy, on and as of the date hereof and the Initial Closing Date, of
the representations and warranties of the Company contained herein, to the
accuracy of the statements of the Company and their respective officers made in
any certificates delivered pursuant hereto, to the performance by the Company of
its respective obligations hereunder, and, subject to Section 1.1, to each of
                                                      -----------
the following additional terms and conditions:

     5.1  Disclosure; Representations and Warranties.  You shall not have
          ------------------------------------------
discovered and disclosed to the Company on or prior to the Closing Date that any
written material delivered by the Company to you taken as a whole contains any
untrue statement of a fact which is material or omits to state any fact which is
material and is required to be stated therein or is necessary to make the
statements therein not misleading. The representations and warranties of the
Company contained in this Agreement which are not qualified by Material Adverse
Effect shall be correct in all material respects when made and at the time of
such Closing and the representations and warranties of the Company contained in
this Agreement that are qualified by Material Adverse Effect shall be correct
when made and at the time of such Closing; provided, that with respect to any
                                           --------
Closing after the April Closing, such conditions shall apply only to the
Standard Representations.

     5.2  Corporate Proceedings.  All corporate proceedings and other legal
          ---------------------
matters incident to the authorization, form and validity of each of the
Transaction Documents, and all other legal matters relating to the Transaction
Documents and the transactions contemplated thereby, shall be reasonably
satisfactory in all material respects to you, and the Company shall have
furnished to you all documents and information that you or your counsel may
reasonably request to enable them to pass upon such matters.

                                      -14-
<PAGE>

     5.3  Opinions.  Each of Cadwalader, Wickersham & Taft and Mintz Levin Cohn
          --------
Ferris Glovsky and Popeo, P.C., shall have furnished to you its written opinion,
as counsel to the Company, addressed to you and dated the Closing Date, in form
and substance reasonably satisfactory to you addressing the matters set forth in
Exhibit B, and Wiley, Rein & Fielding shall have furnished to you its written
---------
opinion, as special communications counsel to the Company, addressed to you and
dated as of the Closing Date, in form and substance reasonably satisfactory you
addressing the matters set forth in Exhibit C.
                                    ---------

     5.4  Registration Rights Agreement.  You shall have received a counterpart
          -----------------------------
of the Registration Rights Agreement which shall have been executed and
delivered by a duly authorized officer of the Company.

     5.5  Indenture; Notes.  The Indenture shall have been duly executed and
          ----------------
delivered by the Company and the Trustee and shall be in full force and effect,
and the Notes shall have been duly executed and delivered by the Company and
duly authenticated by the Trustee.

     5.6  Material Adverse Change.  Except for the Merger, the Telecorp Wireless
          -----------------------
Notes and the Tritel 2011 Notes, subsequent to July 10, 2000, there shall not
have been any change in the capital stock or long-term debt or any change, or
any development involving a prospective change in or affecting the condition
(financial or otherwise), results of operations, business or prospects of the
Company and its subsidiaries taken as a whole, the effect of which, in any such
case described above, is, in your reasonable judgment, so material and adverse
as to make it impracticable or inadvisable to proceed with the sale or delivery
of the Notes on the terms and in the manner contemplated by this Agreement.

     5.7  Downgrade of Debt Securities.  Subsequent to July 10, 2000, (i) no
          ----------------------------
downgrading shall have occurred in the rating accorded any of the Company's or
its subsidiaries' debt securities or preferred stock by any "nationally
recognized statistical rating organization", as such term is defined by the
Commission for purposes of Rule 436(g)(2) of the rules and regulations under the
Securities Act, and (ii) no such organization shall have publicly announced that
is has under surveillance or review (other than an announcement with positive
implications of a possible upgrading), its rating of any of the Company's or any
of its subsidiaries' debt securities or preferred stock.

     5.8  Procurement Contract.  The Procurement Contract (including Amendment
          --------------------
No. 8 thereto dated as of July 14, 2000) shall be a legal, valid and binding
obligation of the Company enforceable in accordance with its terms, shall be in
full force and effect and no default or breach by the Company shall have
occurred thereunder which is continuing or the Company shall have satisfied all
its obligations (including its purchase commitments) pursuant to the Procurement
Contract.

     5.9  Consents, Agreements.  The Company shall have obtained all consents
          --------------------
and waivers under (a) any term of any agreement or instrument to which it is a
party or by which it or any of its properties or assets are bound including,
without limitation, any consents or waivers required under the TeleCorp Wireless
Credit Agreement including the TeleCorp/Tritel Consent, or (b) any term of any
applicable law, ordinance, rule or regulation of any

                                      -15-
<PAGE>

Governmental Authority or any term of any applicable order, judgment or decree
of any court, arbitrator or Governmental Authority, in each case, necessary or
appropriate in connection with this Agreement, the Equity Securities Purchase
Agreement and the Procurement Contract, and such consents and waivers shall be
in full force and effect on the Closing Date. A complete and correct copy of
each such consent and waiver shall have been delivered to you.

     5.10  No Actions Pending.  There shall be no suit, action, investigation,
           ------------------
inquiry or other proceeding by or before any Governmental Authority or any other
Person or any other legal or administrative proceeding, pending or, to the
Company's knowledge, threatened, which questions the validity or legality of the
transactions contemplated hereunder or the payment, prepayment, administration,
sale or other disposition of the Notes or performance by the Company of its
obligations under this Agreement, the Indenture, the Registration Rights
Agreement or the Notes and seeks damages or injunctive or other equitable relief
in connection therewith.

     5.11  Purchase Permitted By Applicable Law.  On the Closing Date, your
           ------------------------------------
purchase of Notes (a) shall be permitted by the laws and regulations of each
jurisdiction to which you are subject and (b) shall not subject you to any tax
(other than taxes based on net income) or penalty.

     5.12  Fees.  The fees required to be paid on the Closing Date under
           ----
Section 1.3 shall have been paid.
-----------

     5.13  Documentation.  All opinions, letters, evidence and certificates
           -------------
mentioned above or elsewhere in this Agreement shall be deemed to be in
compliance with the provisions hereof only if they are in form and substance
reasonably satisfactory to you.

     5.14  No Events of Default.  There shall not have occurred and be
           --------------------
continuing any event of default under the Notes or under any debt instrument of
TeleCorp Wireless, Tritel, Inc. or any of their respective subsidiaries if the
total amount of indebtedness issued thereunder exceeds $100,000,000.

     6.  Termination.  You may terminate the obligations hereunder, in your
         -----------
absolute discretion, by notice given to and received by the Company prior to
delivery of and payment for the Notes if, prior to that time, the events
described in Section 5.8 shall have occurred and be continuing.
             -----------

     7.  Special Event of Default.  Until the occurrence of any of the Special
         ------------------------
Default Release Conditions, the parties hereto agree and the Trustee
acknowledges that it shall be an Event of Default under the Indenture and that
the Trustee or the Holders of at least 25% in aggregate principal amount at
maturity of the then outstanding Notes may exercise any of the remedies
contemplated thereunder if the Company shall be in default of or shall breach
any of its obligations under the Procurement Contract (provided that you shall
                                                       --------
have given TeleCorp Wireless any notice of such default as required under the
Procurement Contract and any cure period under the Procurement Contract shall
have expired) and as a result thereof such Procurement Contract shall have
terminated.  The Company and you agree that if the Trustee shall fail to execute
the acknowledgment set forth at the foot of this Agreement on or prior to the

                                      -16-
<PAGE>

Initial Closing Date, the Indenture shall be amended to include the provisions
contained in the first sentence of this Section; provided that, as between the
                                                 --------
Company and you, this Agreement (notwithstanding the lack of such
acknowledgement) shall be in full force and effect.

     8.  Definitions.  As used herein the following terms have the following
         -----------
respective meanings:

         Affiliate:  any Person directly or indirectly controlling or
         ---------
controlled by or under common control with another Person or any subsidiary of
such other Person; provided that, for purposes of this definition, "control"
                   --------
(including, with correlative meanings, the terms "controlled by" and "under
common control with"), as used with respect to any Person, shall mean the
possession, directly or indirectly, of the power to direct or cause the
direction of the management and policies of such Person, whether through the
ownership of voting securities or by contract or otherwise.

         Business Day: the meaning specified in the Indenture.
         ------------

         Closing Date:  the Initial Closing Date, the October Closing Date and
         ------------
each Market Note Closing Date.

         Default:  the meaning specified in the Indenture.
         -------

         Event of Default:  the meaning specified in the Indenture.
         ----------------

         Governing Documents: as to any Person, its articles or certificate of
         -------------------
incorporation and by-laws, its partnership agreement, its certificate of
formation and operating agreement, or the other organizational or governing
documents of such Person.

         Governmental Authority:  any nation or government, any state or other
         ----------------------
political subdivision thereof and any entity exercising executive, legislative,
judicial, regulatory or administrative functions of or pertaining to government.

         Holders:  the meaning specified in the Indenture.
         -------

         Indebtedness:  the meaning specified in the Indenture.
         ------------

         Initial Closing Date:  April 6, 2001.
         --------------------

         Iowa Market:  the meaning given to such term in the Procurement
         -----------
Contract.

         Lien:  the meaning specified in the Indenture.
         ----

         Market Note Closing Date:  the date specified from time to time for
         ------------------------
the purchase of Market Notes in Market Note Notices.

         Merger:  the meaning given to such term in the Merger Agreement.
         ------

                                      -17-
<PAGE>

          Merger Agreement:  the Agreement and Plan of Reorganization and
          ----------------
Contribution dated as of February 28, 2000 by and among TeleCorp Wireless,
Tritel and AT&T Wireless, as amended.

          Note Purchase Agreement:  The Note Purchase Agreement dated as of May
          -----------------------
11, 1998, as amended and restated on October 21, 1999, between TeleCorp Wireless
and Lucent Technologies Inc., as further amended.

          October Closing Date:  October 1, 2001.
          --------------------

          Person:  an individual, a partnership, an association, a joint
          ------
venture, a corporation, a limited liability Company, a business, a trust, an
unincorporated organization or a government or any department, agency or
subdivision thereof.

          Procurement Contract:  The General Agreement for Purchase of Personal
          --------------------
Communication Systems and Services effective as of May 12, 1998 between TeleCorp
Wireless, Inc. (formerly known as TeleCorp PCS, Inc.) and you as Vendor (the

"Vendor"), as amended.
-------

          Reasonable best efforts:  shall mean prompt, substantial and
          -----------------------
persistent efforts as a prudent Person desirous of achieving a result would use
in a similar circumstances; provided that the Company, shall be required to
                            --------
expend only such resources as are commercially reasonable in the applicable
circumstances.

          Special Default Release Conditions:  the first to occur of the
          ----------------------------------
following events:  (i) none of the Notes are then held by you or your
affiliates, (ii) the Company shall have acquired from the Vendor, shall have
deployed and shall have paid all amounts to the Vendor with respect to one
mobile switching center and fifty base stations for Iowa Markets and one mobile
switching center and one hundred base stations for Wisconsin Markets and (iii)
the Exchange Notes shall have been issued.

          Standard Representations:  the representations and warranties
          ------------------------
contained in Sections 2.1, 2.3 through 2.8, 2.11(b), 2.15, 2.24, 2.25 and 2.32.
             ------------  ---         ---  -------  ----  ----  ----     ----

          Subsidiary:  with respect to any Person, any corporation or other
          ----------
entity at least 50% (by number of votes) of the Voting Stock or voting power of
which is at the time owned by such Person or by one or more subsidiaries or by
such Person and one or more subsidiaries.  Unless otherwise indicated, all
references to subsidiaries shall be deemed reference to the Company's
subsidiaries.

          Telecorp Wireless Notes: the 10 5/8% Senior Subordinated Notes issued
          -----------------------
by TeleCorp Wireless pursuant to an Indenture dated July 14, 2000

          TeleCorp Wireless:  TeleCorp Wireless, Inc. (formerly known as
          -----------------
TeleCorp PCS, Inc.), a Delaware corporation.

          TeleCorp/Tritel Wireless Consent:  the written consent of the Lenders
          --------------------------------
under the TeleCorp Wireless Credit Agreement or the Tritel Credit Agreement
permitting TeleCorp Wireless or Tritel, as the case may be, to make Restricted
Payments (as defined under the

                                      -18-
<PAGE>

TeleCorp Wireless Credit Agreement or the Tritel Credit Agreement, as the case
may be ) to the Company or any of its subsidiaries (as directed by the Company),
in cash, and without restriction, in an amount equal to the proceeds of any
equity investment contributed by the Company directly or indirectly to Tritel or
TeleCorp Wireless or any of their respective subsidiaries from the proceeds of
the Notes (the amount of such equity investment to be determined in good faith
by the board of directors of the Company), which dividends shall be payable not
later than the first date on which a cash interest payment is required to be
made in respect of the Notes, such amount not to exceed the amount of excess
cash flow generated after the date such equity investment first occurs or the
amount of scheduled payments of principal and interest).

          TeleCorp Wireless Credit Agreement:  the Credit Agreement dated as of
          ----------------------------------
July 17, 1998, as amended, waived or otherwise modified from time to time, among
TeleCorp Wireless, the financial institutions named therein as lenders, The
Chase Manhattan Bank, as Administrative Agent and Issuing Bank, TD Securities
(USA) Inc., as Syndication Agent, and Bankers Trust Company, as Documentation
Agent.

          Transactional Representations:  the representation and warranties
          -----------------------------
contained in Sections 2.10, 2.13, 2.14, 2.16 through 2.23, 2.27 through 2.30 and
                      ----  ----  ----  ----         ----  ----         ----
2.33.
----

          Tritel: Tritel, Inc., a Delaware corporation.
          ------

          Tritel 2011 Notes:  the 10 3/8% Senior Subordinated Notes due 2011
          -----------------
issued by Tritel PCS, Inc. pursuant to an Indenture dated as of January 24,
2001.

          Tritel Credit Agreement:  the meaning specified in the Indenture.
          -----------------------

          Wisconsin Market:  the meaning specified in the Procurement  Contract.
          ----------------

          Voting Stock:  with reference to any corporation, stock of any class
          ------------
or classes (or equivalent interests), if the holders of the stock of such class
or classes (or equivalent interests) are ordinarily, in the absence of
contingencies, entitled to vote for the election of the directors (or Persons
performing similar functions) of such corporation, even though the right so to
vote has been suspended by the happening of such a contingency.

     9.  Fees and Expenses.  Whether or not the transactions contemplated by
         -----------------
this Agreement shall be consummated, the Company will pay all reasonable
expenses in connection with such transactions and in connection with any
amendments or waivers (whether or not the same become effective) under or in
respect of this Agreement, the Indenture, the Notes and the Registration Rights
Agreements, including, without limitation: (a) the cost and expenses of
preparing and reproducing this Agreement, the Indenture and the Registration
Rights Agreement and the Notes, of furnishing all opinions by counsel for the
Company (including any opinions requested by your special counsel as to any
legal matter arising hereunder) and all certificates on behalf of the Company,
and of the Company's performance of and compliance with all agreements and
conditions contained herein on its part to be performed or complied with; (b)
the cost of delivering to your principal office, insured to your satisfaction,
the Notes sold to you hereunder and any Notes delivered to you upon any
substitution of Notes pursuant to the terms of the Indenture, and of your
delivering any Notes, insured to your satisfaction, upon any such

                                      -19-
<PAGE>

substitution; (c) the costs of preparing the Exchange Offer Registration
Statement, the Shelf Registration Statement, if any, and the Exchange Notes as
set forth in the Registration Rights Agreements; (d) the reasonable expenses and
disbursements of special counsel for the Holders of the Notes in connection with
such transactions and any such amendments or waivers; (e) the fees and expenses
of the Trustee and any paying agent (including related fees and expenses of
counsel to such parties) and (f) the reasonable out-of-pocket expenses incurred
by you in connection with such transactions and any such amendments or waivers.
The Company also will pay, and will save you and each Holder of any Notes
harmless from, all claims in respect of the fees, if any, of brokers and finders
and any and all liabilities with respect to any taxes (including interest and
penalties but excluding taxes measured by or payable with respect to gross or
net income) which may be payable in respect of the execution and delivery of
this Agreement, the Indenture, the Registration Rights Agreement, the issue of
the Notes and any amendment or waiver under or in respect of this Agreement, the
Indenture, the Registration Rights Agreement and the Notes. The obligation of
the Company under this Section 9 shall survive any disposition or payment of the
                       ---------
Notes and the termination of this Agreement.

     10.  Survival of Representations and Warranties.  All representations and
          ------------------------------------------
warranties contained in this Agreement or made in writing by or on behalf of the
Company in connection with the transactions contemplated by this Agreement shall
survive the execution and delivery of this Agreement, any investigation at any
time made by you or on your behalf, the purchase of the Notes by you under this
Agreement and any disposition or payment of the Notes.  All statements contained
in any certificate or other instrument delivered by or on behalf of the Company
pursuant to this Agreement shall be deemed representations and warranties of the
Company under this Agreement.

     11.  Amendments and Waivers.  Any term of this Agreement may be amended and
          ----------------------
the observance of any term of this Agreement may be waived (either generally or
in a particular instance and either retroactively or prospectively) only with
the written consent of the Company and you.

     12.  Notices, etc.  Except as otherwise provided in this Agreement, notices
          -------------
and other communications under this Agreement shall be in writing and shall be
delivered by hand or courier service, or mailed by registered or certified mail,
return receipt requested, addressed, (a) if to you, at the address set forth in
Schedule A or at such other address as you shall have furnished to the Company
----------
in writing, with respect to payments on Notes held by you or your nominee, or
(b) if to any other Holder of any Note, at such address as such other Holder
shall have furnished to the Company in writing, or, until any such other Holder
so furnishes to the Company an address, then to and at the address of the last
Holder of such Notes who has furnished an address to the Company, or (c) if to
the Company, at its address set forth at the beginning of this Agreement, to the
attention of the Chief Financial Officer, with copies to Cadwalader, Wickersham
& Taft, 100 Maiden Lane, New York, N.Y. 10038, Attn: Brian Hoffmann, and
McDermott, Will & Emery, 28 State Street, Boston, MA 02109, Attn: John B.
French, or at such other address, or to the attention of such other officer, as
the Company shall have furnished to you and each such other Holder in writing.
Any notice so addressed and delivered by hand or courier shall be deemed to be
given when received, and any notice so addressed and mailed by registered or
certified mail shall be deemed to be given three Business Days after being so
mailed.

                                      -20-
<PAGE>

     13.  Indemnification.  The Company will indemnify and hold harmless each
          ---------------
Holder of Notes and each person who controls a Holder within the meaning of the
Securities Act or the Exchange Act and each of the Holder's subsidiaries and
each Holder's respective directors, officers, employees, agents and advisors
(any and all of whom are referred to as the "Indemnified Party") from and
                                             -----------------
against any and all losses, claims, damages and liabilities, whether joint or
several (including all legal fees or other expenses reasonably incurred by
counsel for any Indemnified Party in connection with the preparation for or
defense of any pending or threatened third party claim, action or proceeding,
whether or not resulting in any liability), to which such Indemnified Party may
become subject (whether or not such Indemnified Party is a party thereto) under
any applicable federal or state law or otherwise, caused by or arising out of,
this Agreement or any transaction contemplated hereby or thereby (including,
without limitation, any of the foregoing relating to the violation of, non-
compliance with or liability under any environmental law applicable to the
operations of the Company or its subsidiaries), other than, with respect to any
Indemnified Party, losses, claims, damages or liabilities that are the result of
the gross negligence or willful misconduct of such Indemnified Party.

          Promptly after receipt by an Indemnified Party of notice of any claim,
action or proceeding with respect to which an Indemnified Party is entitled to
indemnity hereunder, such Indemnified Party will notify the Company of such
claim or the commencement of such action or proceeding; provided that the
                                                        --------
failure of an Indemnified Party to give notice as provided herein shall not
relieve the Company of its obligations under this Section 13 with respect to
                                                  ----------
such Indemnified Party, except to the extent that the Company is actually
prejudiced by such failure. The Company will assume the defense of such claim,
action or proceeding and will employ counsel reasonably satisfactory to the
Indemnified Party and will pay the fees and expenses of such counsel.
Notwithstanding the preceding sentence, the Indemnified Party will be entitled,
at the expense of the Company, to employ counsel separate from counsel for the
Company and for any other party in such action if the Indemnified Party
reasonably determines that a conflict of interest or other reasonable basis
exists which makes representation by counsel chosen by the Company not
advisable, but the Company will not be obligated to pay the fees and expenses of
more than one counsel for all Indemnified Parties.

          The agreements in this Section 13 shall survive repayment of the Notes
                                 ----------
and all other amounts payable hereunder.

     14.  Successors and Assigns.  This Agreement shall be binding upon and
          ----------------------
inure to the benefit of the Company, the Holders and their respective successors
and assigns, except that the Company may not assign or transfer any of its
rights or obligations under this Agreement, the Indenture, the Registration
Rights Agreement or the Notes without the prior written consent of each Holder.

     15.  Miscellaneous.  This Agreement shall be binding upon and inure to the
          -------------
benefit of and be enforceable by the respective successors and assigns of the
parties hereto, whether so expressed or not, and, in particular, shall inure to
the benefit of and be enforceable by any Holder or Holders at the time of the
Notes or any part thereof.  This Agreement embodies the entire agreement and
understanding between you and the Company and supersedes all prior agreements
and understandings relating to the subject matter hereof.  THIS AGREEMENT SHALL
BE

                                      -21-
<PAGE>

CONSTRUED AND ENFORCED IN ACCORDANCE WITH AND GOVERNED BY THE LAWS OF THE STATE
OF NEW YORK, WITHOUT REGARD TO THE PRINCIPLES OF CONFLICT OF LAWS THEREOF, OTHER
THAN SECTION 5-1401 OF THE GENERAL OBLIGATIONS LAW OF THE STATE OF NEW YORK. The
headings in this Agreement are for purposes of reference only and shall not
limit or otherwise affect the meaning hereof. This Agreement may be executed in
any number of counterparts, each of which shall be an original, but all of which
together shall constitute one instrument.

     16.  Submission To Jurisdiction; Waivers.  The Company hereby irrevocably
          -----------------------------------
and unconditionally:

     (a)  SUBMITS FOR ITSELF AND ITS PROPERTY IN ANY LEGAL ACTION OR PROCEEDING
RELATING TO THIS AGREEMENT, OR FOR RECOGNITION AND ENFORCEMENT OF ANY JUDGMENT
IN RESPECT THEREOF, TO THE NON-EXCLUSIVE GENERAL JURISDICTION OF THE COURTS OF
THE STATE OF NEW YORK, THE COURTS OF THE UNITED STATES OF AMERICA FOR THE
SOUTHERN DISTRICT OF NEW YORK, AND APPELLATE COURTS FROM ANY THEREOF;

     (b)  CONSENTS THAT ANY SUCH ACTION OR PROCEEDING MAY BE BROUGHT IN SUCH
COURTS AND WAIVES ANY OBJECTION THAT IT MAY NOW OR HEREAFTER HAVE TO THE VENUE
OF ANY SUCH ACTION OR PROCEEDING IN ANY SUCH COURT OR THAT SUCH ACTION OR
PROCEEDING WAS BROUGHT IN AN INCONVENIENT COURT AND AGREES NOT TO PLEAD OR CLAIM
THE SAME;

     (c)  AGREES THAT SERVICE OF PROCESS IN ANY SUCH ACTION OR PROCEEDING MAY BE
EFFECTED BY MAILING A COPY THEREOF BY REGISTERED OR CERTIFIED MAIL (OR ANY
SUBSTANTIALLY SIMILAR FORM OF MAIL), POSTAGE PREPAID, TO THE COMPANY AT ITS
ADDRESS SET FORTH IN SECTION 12 OR AT SUCH OTHER ADDRESS OF WHICH YOU SHALL HAVE
                     ----------
BEEN NOTIFIED PURSUANT THERETO;

     (d)  AGREES THAT NOTHING CONTAINED HEREIN SHALL AFFECT THE RIGHT TO EFFECT
SERVICE OF PROCESS IN ANY OTHER MANNER PERMITTED BY LAW OR SHALL LIMIT THE
RIGHT TO SUE IN ANY OTHER JURISDICTION; AND

     (e)  WAIVES, TO THE MAXIMUM EXTENT NOT PROHIBITED BY LAW, ANY RIGHT IT MAY
HAVE TO CLAIM OR RECOVER IN ANY LEGAL ACTION OR PROCEEDING REFERRED TO IN THIS
SECTION 16 ANY SPECIAL, EXEMPLARY, PUNITIVE OR CONSEQUENTIAL DAMAGES.
----------

     17.  WAIVERS OF JURY TRIAL.  THE COMPANY AND YOU HEREBY IRREVOCABLY AND
          ---------------------
UNCONDITIONALLY WAIVE TRIAL BY JURY IN ANY LEGAL ACTION OR PROCEEDING RELATING
TO THIS AGREEMENT AND FOR ANY COUNTERCLAIM THEREIN.

                                      -22-
<PAGE>

          If you are in agreement with the foregoing, please sign the form of
agreement on the accompanying counterparts of this letter and return one of the
same to the Company, whereupon this letter shall become a binding agreement
between you and the Company.

                                 Very truly yours,

                                 TELECORP PCS, INC.

                                 By: /s/ Thomas H. Sullivan
                                    ____________________________
                                    Title:  Executive Vice President
                                            and Chief Financial Officer
The foregoing Agreement is
hereby agreed to as of the
date thereof.

LUCENT TECHNOLOGIES INC.

By: /s/ Robert Grant
   ______________________
   Title:  Director

Solely for purpose of Section 7
Acknowledged and Agreed
FIRSTAR BANK, N.A.
as Trustee

By: /s/ Frank Leslie
   ______________________
   Title:  Vice President
<PAGE>

                                   SCHEDULE A
                                   ----------

                             PURCHASER INFORMATION

Lucent Technologies Inc.
600 Mountain Avenue
Murray Hill, New Jersey 07974
<PAGE>

                                   EXHIBIT A
                                   ---------

                               PURCHASE AGREEMENT
<PAGE>

                                  EXHIBIT B-1
                                  -----------

                             FORM LEGAL OPINION OF
                         CADWALADER, WICKERSHAM & TAFT
<PAGE>

                                  EXHIBIT B-2
                                  -----------

                             FORM LEGAL OPINION OF
                MINTZ LEVIN COHN FERRIS GLOVSKY AND POPEO, P.C.
<PAGE>

                                   EXHIBIT C
                                   ---------

                             FORM LEGAL OPINION OF
                             WILEY, REIN & FIELDING
<PAGE>

                                   EXHIBIT D
                                   ---------

                                 FORM INDENTURE

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