<PAGE>   1
                                                                   EXHIBIT 10.98

                                VOTING AGREEMENT

        VOTING AGREEMENT, dated as of February 25, 2000 (this "Agreement"), by
and among VOICESTREAM WIRELESS HOLDING CORPORATION, a Delaware corporation
("VoiceStream Holdings"), and the individuals and entities set forth on Schedule
I hereto (each, a "Stockholder" and collectively, the "Stockholders").

        WHEREAS, Omnipoint Corporation, a Delaware corporation ("Omnipoint"),
VoiceStream Wireless Corporation, a Washington corporation ("VoiceStream") and
VoiceStream Holdings are parties to an Agreement and Plan of Reorganization,
dated as of June 23, 1999, (as the same has been amended or may hereafter be
amended from time to time, the "Omnipoint Reorganization Agreement") pursuant to
which, among other things, wholly owned subsidiaries of VoiceStream Holdings
will be merged with and into each of Omnipoint and VoiceStream (such mergers,
together with the related transactions contemplated by the Omnipoint
Reorganization Agreement, being referred to herein collectively as the
"Omnipoint Reorganization");

        WHEREAS, each Stockholder is the Beneficial Owner of the number of
shares of VoiceStream Holdings Common Stock (the "Shares") set forth opposite
such Stockholder's name in Schedule I hereto;

        WHEREAS, VoiceStream and certain of the Stockholders are parties to that
certain Voting Agreement, dated May 3, 1999 (the "Original Voting Agreement");

        WHEREAS, as a condition to consummating the Omnipoint Reorganization,
the parties to the Original Voting Agreement have agreed to terminate the
Original Voting Agreement and enter into this Agreement;

        WHEREAS, VoiceStream, VoiceStream Holdings, VoiceStream Subsidiary III
Corporation, a Delaware corporation ("Merger Sub"), Aerial Communications, Inc.,
a Delaware corporation ("Aerial"), and Telephone and Data Systems, Inc., a
Delaware corporation ("TDS"), are parties to an Agreement and Plan of
Reorganization, dated as of September 17, 1999 (as the same may be amended from
time to time, the "Aerial Reorganization Agreement") pursuant to which, among
other things, Merger Sub is to be merged with and into Aerial (such merger,
together with the related transactions contemplated by the Aerial Reorganization
Agreement, being referred to herein as the "Aerial Reorganization");

        WHEREAS, upon the consummation of the Aerial Reorganization, it is
contemplated that TDS will execute an agreement whereby it will become a party
to this Agreement as a Stockholder and, if TDS does so execute such an
agreement, the term Stockholder will for all purposes of this Agreement include
TDS; and

        WHEREAS, Sonera Corporation (formerly Sonera Ltd.) ("Sonera") is a
substantial investor in Aerial and, concurrent with the Omnipoint
Reorganization, will invest $500 million into

<PAGE>   2
VoiceStream Holdings through its Subsidiary, Sonera Holding, B.V. For purposes
of this Agreement, Sonera Corporation and Sonera Holding, B.V., shall be deemed
a single Stockholder.

        NOW THEREFORE, in consideration of the foregoing and the mutual
covenants and agreements set forth herein, the parties hereto agree as follows:

        Section 1. Definitions. As used in this Agreement, the following terms
have the meanings set forth below:

        "Beneficially Own" has the meaning set forth in Rule 13d-3 of the rules
and regulations promulgated under the Securities Exchange Act of 1934, as
amended; except that no broker or dealer or any affiliate thereof shall be
deemed to Beneficially Own Shares, the beneficial ownership of which is acquired
in the ordinary course of the activities of a broker or dealer registered under
Section 15 of the Securities Exchange Act of 1934, as amended, including, but
not limited to, the acquisition of beneficial ownership of such securities as a
result of any market-making or underwriting activities (including any Shares
acquired for the investment account of a broker or dealer in connection with
such underwriting activities), or the exercise of investment or voting
discretion authority over any of its customer accounts, or the acquisition in
good faith of such securities in connection with the enforcement of payment of a
debt previously contracted.

        "Board" means the Board of Directors of VoiceStream Holdings.

        "BSF" means Bridge Street Fund 1992, L.P., a Delaware limited
partnership.

        "Business Day" means a day other than a Saturday, Sunday or other day on
which commercial banks in New York City, Hong Kong or Seattle, Washington are
authorized or required by law to close.

        "GS" means The Goldman Sachs Group, Inc., a Delaware corporation.

        "GSC" means BSF, GS, GSCP and SSF.

        "GSCP" means GS Capital Partners, L.P., a Delaware limited partnership.

        "HTL" means Hutchison Telecommunications Limited, a corporation
organized under the laws of Hong Kong.

        "Hutchison" means Hutchison Holdings and Hutchison PCS.

        "Hutchison Holdings" means Hutchison Telecommunications Holdings (USA)
Limited, a British Virgin Islands corporation.

                                       2
<PAGE>   3
        "Hutchison PCS" means Hutchison Telecommunications PCS (USA) Limited, a
British Virgin Islands corporation.

        "Immediate Family" means an individual's spouse, children (including
adopted children), grandchildren and parents.

        "Percentage Ownership" means, as to any Stockholder, the aggregate
percentage of the outstanding Shares Beneficially Owned by such Stockholder,
including for this purpose, Shares Beneficially Owned by such Stockholder's
Permitted Affiliate Transferees.

        "Permitted Affiliate Transferee" means (i) with respect to any
Stockholder who is a natural Person, any member of such Person's Immediate
Family, or any trust for the benefit of, or a partnership all of the partners of
which are, such Person and/or any member of such Person's Immediate Family; (ii)
with respect to any Stockholder which is a limited partnership (a) any Person
that, as of May 13, 1996, was the sole general partner of such Stockholder or
was the sole general partner of the sole general partner of such Stockholder, or
(b) another limited partnership which has a sole general partner, the control of
which sole general partner is held, directly or indirectly, by five (5) or fewer
natural Persons, provided such natural Persons had control at May 13, 1996 of
the sole general partner of such Stockholder; (iii) with respect to Hutchison,
(w) HTL, (x) any Subsidiary of HTL, or (y) any other entity acceptable to
Stockholders (other than Hutchison and its Permitted Affiliate Transferees)
holding at least a majority of the Shares owned by all Stockholders (other than
Hutchison and its Permitted Affiliate Transferees) in which HTL owns, directly
or indirectly, more than 40% of the outstanding voting power, or (z) in the case
of any Person referred to in clause (w), (x) or (y), Hutchison; (iv) with
respect to Sonera, any Subsidiary of Sonera or any other entity acceptable to
Stockholders (other than Sonera and its Permitted Affiliate Transferees) in
which Sonera owns, directly or indirectly, more than 40% of the outstanding
voting power and of which Sonera and its Subsidiaries are collectively the
largest shareholder; and (v) with respect to TDS, any Subsidiary of TDS or any
other entity acceptable to Stockholders (other than TDS and its Permitted
Affiliate Transferees) in which TDS owns, directly or indirectly, more than 40%
of the outstanding voting power and of which TDS and its Subsidiaries are
collectively the largest shareholder. For purposes of this definition, "control"
shall mean ownership of at least 51% of the equity interest in, and at least 51%
of the voting power on all matters in, an entity or, if applicable, the sole
general partner of such entity.

        "Person" means an individual, corporation, association, partnership,
trust or estate, an unincorporated organization, a joint venture, a government
or any agency or political subdivision thereof, or any other entity of whatever
nature.

        "Qualified Sonera Designee" means an individual designated by Sonera,
provided that VoiceStream Holdings shall have the right to approve such
designee, which approval shall not be unreasonably withheld, so long as such
individual's membership on the Board shall not cause any violation of any
federal anti-trust law or any other federal or state law.

                                       3
<PAGE>   4
        "Qualified TDS Designee" means an individual who is not an officer,
director, management level employee or affiliate (as defined in the Securities
Exchange Act of 1934) of TDS, or of any Person in which TDS or any affiliate of
TDS has an "attributable interest" (as defined by applicable FCC rules and
regulations) designated by TDS provided that VoiceStream Holdings shall have the
right to approve the designee, which approval shall not be unreasonably
withheld.

        "Sonera" means Sonera Corporation, a limited liability company organized
under the laws of Finland, and its wholly-owned Subsidiaries, including Sonera
Holding, B.V., a company organized under the laws of the Netherlands.

        "Sonera Investor Agreement" means the Investor Agreement, dated as of
September 17, 1999, among Sonera Corporation, VoiceStream and VoiceStream
Holdings.

        "SSF" means Stone Street Fund 1992, L.P., a Delaware limited
partnership.

        "Subsidiary" means, as to any Person, another Person which is an entity
as to which such Person owns more than 50% of the outstanding voting power.

        "Transfer" means any sale, assignment, pledge, hypothecation, gift or
other transfer, disposition or encumbrance of any interest (and includes an
exchange of Shares in a merger, consolidation or similar transaction).

        Section 2. Termination of Voting Agreements. The Original Voting
Agreement and Sections 6(a) and 6(b) of the Sonera Investor Agreement
automatically and without further action by any Person shall each be terminated
and of no further force or effect upon the effectiveness of this Agreement.

        Section 3. Agreement to Vote by Stockholders.

        (a)     Each Stockholder (and its Permitted Affiliate Transferees)
hereby agrees to vote (or cause to be voted) all Shares, and any other voting
securities of VoiceStream Holdings, then Beneficially Owned by such Stockholder
(whether issued heretofore or hereafter) that such Stockholder owns or has the
right to vote, in person or by proxy (and shall take all other necessary or
desirable actions within such Stockholder's (or its Permitted Affiliate
Transferees') control, including attendance at meetings in person or by proxy
for purposes of obtaining a quorum and execution of written consents in lieu of
meetings), in favor of the election and continuation in office of the following
sixteen (16) (or, upon completion of the Aerial Reorganization, seventeen (17))
members of the Board (subject to adjustments to such number of directors, as
provided below):

                (i)     John Stanton, as long as he is the chief executive
officer of VoiceStream Holdings;


                                       4
<PAGE>   5
                (ii)    One (1) member designated by John Stanton, so long as he
or his Permitted Affiliate Transferees Beneficially Own at least 4,500,000
Shares;

                (iii)   Four (4) members designated by Hutchison PCS (or if
Hutchison PCS has Transferred all of its Shares to Permitted Affiliate
Transferees of Hutchison PCS, four (4) designees of such Permitted Affiliate
Transferees) and its affiliated entities. Such number of designees shall be
subject to increases or decreases (rounded to the nearest whole number and
subject to Section 3(a)(C) hereof) depending upon increases or reductions in
Hutchison PCS's (and its Permitted Affiliate Transferees') Percentage Ownership
of outstanding Shares, including without limitation Shares issuable to Hutchison
PCS (and its Permitted Affiliate Transferees) upon conversion of the 2.5%
Convertible Junior Preferred Stock, without par value, of VoiceStream Holdings,
purchased by Hutchison PCS pursuant to that certain Stock Subscription Agreement
dated June 23, 1999, by and among VoiceStream Holdings, HTL and Hutchison PCS.
Hutchison PCS shall have the right to designate additional members (the Board
shall be expanded by one (1) member to accommodate each such new designee unless
there are vacancies on the Board and the Board determines to fill any vacancies
with such designees) so that the percentage of the entire Board represented by
Hutchison PCS's designees (rounded to the nearest whole number) shall be
proportionate to Hutchison PCS's (and its Permitted Affiliate Transferees')
aggregate Percentage Ownership;

                (iv)    One (1) member designated by GSC and its Permitted
Affiliate Transferees, so long as such entities Beneficially Own at least
4,500,000 Shares;

                (v)     Four (4) members who were on the Board of Directors of
Omnipoint prior to the Omnipoint Reorganization and who are selected by
Omnipoint to serve (the following persons have been designated by Omnipoint to
serve as directors: Douglas G. Smith, Richard L. Fields, James N. Perry, Jr. and
James J. Ross; such Persons being collectively referred to as the "Omnipoint
Designees") during the period from the closing of the Omnipoint Reorganization
until and including the second annual meeting of stockholders of VoiceStream
Holdings taking place after the closing of the Omnipoint Reorganization (it
being understood that such four (4) members shall serve until such time as the
term of office of the directors elected at such second annual meeting
terminates);

                (vi)    One (1) Qualified Sonera Designee designated by Sonera
and its Permitted Affiliate Transferees so long as such entities Beneficially
Own at least 4,500,000 Shares; provided, however, that if the Aerial
Reorganization is consummated and Sonera Beneficially Owns more than 9,800,000
Shares and TDS Beneficially Owns less than 4,500,000 Shares, the number of
Qualified Sonera Designees that Sonera will be entitled to designate will be two
(2);

                (vii)   If the Aerial Reorganization is consummated and TDS and
VoiceStream Holdings execute the agreement in the form attached hereto as
Exhibit A whereby TDS becomes a party to this Agreement as a Stockholder, one
(1) Qualified TDS Designee designated by TDS and its Permitted Affiliate
Transferees so long as such entities Beneficially Own at least

                                       5
<PAGE>   6
4,500,000 Shares, such director to be appointed to the Board by action of the
Board by the later of (x) the closing of the Aerial Reorganization or (y)
promptly after TDS designates a Qualified TDS Designee; provided, however, that
if TDS Beneficially Owns more than 9,800,000 Shares and Sonera Beneficially Owns
less than 4,500,000 Shares, the number of Qualified TDS Designees that TDS will
be entitled to designate will be two (2); and

                (viii)  The remaining members of the Board as selected by a
majority vote of the persons selected as described in subsections (i) through
(vii) above.

        No designee to the Board shall be removed from the Board (except removal
for cause under applicable law) without the written consent of the Stockholder
or group of Stockholders that has the right to designate such Person to the
Board (or, if such Stockholder or group of Stockholders has Transferred all of
their Shares to Permitted Affiliate Transferees of such Stockholder or group of
Stockholders, without the written consent of Permitted Affiliate Transferees
holding a majority of the Shares owned by all of such Permitted Affiliate
Transferees), or, in the case of the Omnipoint Designees, without the consent of
a majority of the Board of Directors of Omnipoint as such Board of Directors
existed immediately prior to the Omnipoint Reorganization (the "Old Omnipoint
Board"). Any Stockholder or group of Stockholders (or, if such Stockholder or
group of Stockholders has Transferred all of their Shares to Permitted Affiliate
Transferees of such Stockholder or group of Stockholders, Permitted Affiliate
Transferees holding a majority of the Shares owned by all of such Permitted
Affiliate Transferees) or, in the case of the Omnipoint Designees, a majority of
the Old Omnipoint Board, that has the right to designate any member(s) of the
Board shall have the right to replace any member(s) so designated by it (whether
or not such member is removed from the Board with or without cause or ceases to
be a member of the Board by reason of death, disability or for any other reason)
upon written notice to VoiceStream Holdings and the other members of the Board,
which notice shall set forth the name of the member(s) being replaced and the
name of the new member(s). Each of the Stockholders (and each of their
respective Permitted Affiliate Transferees) agrees that it will vote, or cause
to be voted, all of the Shares then Beneficially Owned by it (whether now owned
or hereafter acquired ), in person or by proxy (and shall take all other
necessary or desirable actions within such Stockholder's (or its Permitted
Affiliate Transferees's) control including attendance at meetings in person or
by proxy for purposes of obtaining a quorum and execution of written consents in
lieu of meetings), so as to cause, if necessary, the removal of the existing
director previously elected by such Stockholders (and its Permitted Affiliate
Transferees), or previously designated by Omnipoint (in the case of the original
Omnipoint Designees) or by a majority of the Old Omnipoint Board (if the Old
Omnipoint Board designates a replacement for an Omnipoint Designee, such
replacement shall for all purposes of this Agreement be an Omnipoint Designee),
and the election and continuation in office of any successor director designated
by any of the Stockholders (or any of such Stockholder's Permitted Affiliate
Transferees) pursuant to this Section 3(a). Notwithstanding the foregoing,

                (A)     if at any time GSC (and its Permitted Affiliate
Transferees) shall cease to Beneficially Own at least 4,500,000 Shares, then in
such event, GSC (or, if GSC has Transferred


                                       6
<PAGE>   7
all of its Shares to Permitted Affiliate Transferees of GSC, its Permitted
Affiliate Transferees) shall not be entitled to designate any member of the
Board;

                (B)     if at any time John Stanton (and his Permitted Affiliate
Transferees) shall cease to Beneficially Own at least 4,500,000 shares, then in
such event, John Stanton (or, if John Stanton has Transferred all of his Shares
to Permitted Affiliate Transferees of John Stanton, his Permitted Affiliate
Transferees) shall not be entitled to designate any member of the Board (except
that Stanton shall continue to serve on the Board for so long as he holds the
office of Chief Executive Officer of VoiceStream Holdings);

                (C)     if at any time Hutchison PCS (and its Permitted
Affiliate Transferees) shall cease to Beneficially Own at least (i) 9,800,000
Shares, then in such event Hutchison PCS and its Permitted Affiliate Transferees
shall be entitled to designate only one member of the Board; and (ii) 4,500,000
Shares, then in such event, Hutchison PCS and its Permitted Affiliate
Transferees shall not be entitled to designate any member of the Board. In
addition, if Hutchison PCS shall have designated additional director(s) by
reason of an increase in its Percentage Ownership as set forth in Section
3(a)(iii) above, and at any time thereafter the Percentage Ownership of
Hutchison PCS (and its Permitted Affiliate Transferees) shall decrease, (i) the
number of designees Hutchison PCS (and its Permitted Affiliate Transferees) are
entitled to designate to the Board shall be reduced so that the percentage of
the entire Board represented by Hutchison PCS's (and its Permitted Affiliate
Transferees') designees (rounded to the nearest whole number) shall be
proportionate to Hutchison PCS's (and its Permitted Affiliate Transferees')
aggregate Percentage Ownership, (ii) any members designated by Hutchison PCS
(and its Permitted Affiliate Transferees) in excess of such number shall be
removed from the Board (any such members to be removed to be designated by
Hutchison or, in the event that Hutchison fails to designate the members to be
removed, by a majority of the members of the Board), and (iii) the Board shall
be reduced in size by the number of members so removed;

                (D)     if at any time Sonera (and its Permitted Affiliate
Transferees) shall cease to Beneficially Own at least (i) 9,800,000 Shares at a
time when Sonera is entitled to designate two (2) directors, then in such event,
Sonera (or, if Sonera has Transferred all of its Shares to Permitted Affiliate
Transferees of Sonera, its Permitted Affiliate Transferees) shall be entitled to
designate only one (1) member of the Board; and (ii) 4,500,000 Shares, then in
such event, Sonera (or, if Sonera has Transferred all of its Shares to Permitted
Affiliate Transferees of Sonera, its Permitted Affiliate Transferees) shall not
be entitled to designate any member of the Board;

                (E)     if the Aerial Reorganization is consummated and TDS and
VoiceStream Holdings execute an agreement in the form attached hereto as Exhibit
A whereby TDS becomes a party to this Agreement as a Stockholder, and at any
time thereafter TDS (and its Permitted Affiliate Transferees) shall cease to
Beneficially Own at least (i) 9,800,000 Shares at a time when TDS is entitled to
designate two (2) directors, then in such event, TDS (or, if TDS has Transferred
all of its Shares to Permitted Affiliate Transferees of TDS, its Permitted
Affiliate Transferees) shall be entitled to designate only one (1) member of the
Board; and (ii) 4,500,000 Shares, then in such event, TDS (or, if TDS has
Transferred all of its Shares to Permitted Affiliate


                                       7
<PAGE>   8
Transferees of TDS, its Permitted Affiliate Transferees) shall not be entitled
to designate any member of the Board;

                (F)     Any vacancies on the Board created by reason of the
provisions of subsections (A) through (E) above shall be filled by the vote of a
majority of the directors then in office (unless such directors determine to
reduce the size of the Board after a vacancy is created) to serve until the next
annual meeting of shareholders of VoiceStream Holdings, and at the next annual
meeting shall be filled by a vote of a plurality of all shareholders of
VoiceStream Holdings (including the Stockholders and their Permitted Affiliate
Transferees); provided, however, that in the event that the size of the Board
shall have increased by reason of Hutchison PCS having the right to designate
additional director(s) and thereafter Hutchison PCS shall cease to have the
right to so designate such additional director(s), the size of the Board shall
be appropriately reduced and each of the Stockholders (and each of their
respective Permitted Affiliate Transferees ) agrees that it will vote, or cause
to be voted, all of the Shares then Beneficially Owned by it (whether now owned
or hereafter acquired), in person or by proxy (and, shall take all other
necessary or desirable actions within such Stockholder's (or its Permitted
Affiliate Transferees') control including attendance at meetings in person or by
proxy for purposes of obtaining a quorum and execution of written consents in
lieu of meetings), to cause such reduction in the Board.

                (G)     Notwithstanding anything to the contrary contained in
this Agreement, Hutchison's right to transfer its right to designate directors
to certain block transferees as set forth in Sections 14 and 15 of the
Shareholders Agreement of VoiceStream Wireless Corporation, dated February 17,
1998, as amended, among Western Wireless Corporation, a Washington corporation,
VoiceStream and Hutchison PCS, shall continue in full force and effect until
terminated in accordance with the terms of such Shareholders Agreement.

                (b)     Notwithstanding anything to the contrary herein, if a
Stockholder shall cease to have the right to designate any director to the Board
pursuant to this Agreement, such Stockholder shall be released in full from all
obligations and shall cease to have any rights under this Agreement; provided,
however, that at the time that the Omnipoint Designees no longer serve on the
Board and there is no further obligation to designate Omnipoint Designees under
Section 3(a)(v) hereof, the following Persons shall be released in full from all
obligations and shall cease to have any rights under this Agreement: Allen &
Company Incorporated, Avance Capital, Avance Capital II, Avance Capital III,
Madison Dearborn Capital Partners, L.P., James N. Perry, Jr., Douglas G. Smith,
Douglas and Gabriela Smith 1995 Family Trust, Richard L. Fields, James J. Ross
and James J. Ross, as Trustee.

        Section 4.  VoiceStream Holdings and Stockholder Covenants.

        (a)     VoiceStream Holdings hereby agrees to use all reasonable efforts
to give effect to the provisions of Section 3 hereof. In this regard,
VoiceStream Holdings shall, subject to the provisions of Section 3 hereof, duly
nominate the designees set forth above, or as may otherwise be designated by a
party hereto pursuant to the terms of Section 3 hereof, for election to the
Board and


                                       8
<PAGE>   9
shall include in any proxy solicitation materials related to the election of
members of the Board such information and recommendations of the Board as are
appropriate, in proxy solicitation materials.

        (b)     Each Stockholder shall vote the Shares then Beneficially Owned
by such Stockholder at any regular or special meeting of the Stockholders or in
any written consent executed in lieu of such a meeting of Stockholders for the
election of such designees. VoiceStream Holdings and each Stockholder shall take
all other actions necessary to ensure that the certificate of incorporation and
by-laws of VoiceStream Holdings or any successor constituent documents as in
effect immediately following the date hereof do not, at any time thereafter,
conflict in any respect with the provisions of this Agreement.

        (c)     At the closing of the Aerial Reorganization, TDS and VoiceStream
Holdings shall enter into the agreement attached hereto pursuant to which TDS
shall become a party to this Agreement, provided that nothing in this Agreement
shall in any way limit, amend or modify any of the terms or provisions of the
Investor Agreement to be entered into among TDS, VoiceStream Holdings and
VoiceStream at such time.

        Section 5. Representations and Warranties of VoiceStream Holdings.
VoiceStream Holdings represents and warrants to each Stockholder as follows:
(i) it has full power and authority to execute, deliver and perform its
obligations under this Agreement; (ii) this Agreement and all transactions
contemplated hereby have been duly and validly authorized by all necessary
action on its part, this Agreement has been duly executed and delivered by it,
and this Agreement constitutes its legal, valid and binding obligation
enforceable against VoiceStream Holdings in accordance with its terms, except as
may be limited by applicable bankruptcy, insolvency, reorganization, moratorium
and other similar laws of general application which may affect the enforcement
of creditors' rights generally and by general equitable principles; and (iii)
neither the execution, delivery or performance of this Agreement by it, nor the
consummation of the transactions contemplated hereby will, with or without the
giving of notice or passage of time or both conflict with, result in a default
or loss of rights (or give rise to any right of termination, cancellation or
acceleration) under, (A) any provision of the certificate of incorporation,
by-laws, partnership agreement or comparable constituent document of it, (B) any
material note, bond, indenture, mortgage, deed of trust, contract, agreement,
lease or other instrument or obligation to which it is a party or by which it or
its properties may be bound or affected or (C) any law, order, judgment,
ordinance, rule, regulation or decree to which it is a party or by which it or
any of its properties are bound or affected.

        Section 6. Representations and Warranties of the Stockholders.

        Each Stockholder, severally, as to such Stockholder, represents and
warrants to the other parties as follows:(i) such Stockholder has full power and
authority to execute, deliver and perform such Stockholder's obligations under
this Agreement; (ii) this Agreement and all transactions contemplated hereby
have been duly and validly authorized by all necessary action on such
Stockholder's part, this Agreement has been duly executed and delivered by such
Stockholder, and this Agreement constitutes such Stockholder's legal, valid and
binding obligation enforceable against


                                       9
<PAGE>   10
such Stockholder in accordance with its terms, except as may be limited by
applicable bankruptcy, insolvency, reorganization, moratorium and other similar
laws of general application which may affect the enforcement of creditors'
rights generally and by general equitable principles; (iii) neither the
execution, delivery or performance of this Agreement by such Stockholder, nor
the consummation of the transactions contemplated hereby will, with or without
the giving of notice or passage of time or both conflict with, result in a
default or loss of rights (or give rise to any right of termination,
cancellation or acceleration) under, (A) if such Stockholder is an entity, any
provision of the certificate of incorporation, by-laws, partnership agreement or
comparable constituent document of such Stockholder, (B) any material note,
bond, indenture, mortgage, deed of trust, contract, agreement, lease or other
instrument or obligation to which such Stockholder is a party or by which such
Stockholder or such Stockholder's properties may be bound or affected or (C) any
law, order, judgment, ordinance, rule, regulation or decree to which such
Stockholder is a party or by which such Stockholder or any of such Stockholder's
properties are bound or affected; and (iv) the Shares listed next to the name of
such Stockholder on Schedule I hereto are the only voting securities of
VoiceStream Holdings Beneficially Owned by such Stockholder.

        Section 7. Effectiveness & Termination. This Agreement shall be
effective as of the effectiveness of the Omnipoint Reorganization and shall
terminate upon the earliest to occur of any of the following events:

        (a)     Upon agreement by all Stockholders then retaining the right to
designate directors under this Agreement and, so long as Omnipoint Designees are
to be designated or are serving pursuant to Section 3(a)(v) hereof, by the
Omnipoint Designees or the Old Omnipoint Board; or

        (b)     The filing by VoiceStream Holdings of a petition in bankruptcy
or the expiration of sixty (60) days after a petition in bankruptcy shall have
been filed against VoiceStream Holdings and such petition shall not have been
stayed or discharged during such sixty (60) day period; or upon the expiration
of sixty (60) days after the commencement of any proceeding under any law for
the relief of debtors seeking the relief or readjustment of VoiceStream
Holdings' indebtedness either through reorganization, winding-up, extension or
otherwise, and such proceedings involving VoiceStream Holdings as debtor shall
not have been vacated or stayed within such sixty (60) day period; or upon the
appointment of a receiver, custodian or trustee for all or substantially all of
VoiceStream Holdings' property, or the making of VoiceStream Holdings of any
general assignment for the benefit of creditors, or the admitting in writing by
VoiceStream Holdings of its inability to pay its debts as they mature; or upon
the voluntary or involuntary liquidation or dissolution of VoiceStream Holdings;
or

        (c)     The Beneficial Ownership of all of the Shares by only one
Stockholder (including its Permitted Affiliate Transferees).

                                       10
<PAGE>   11
Upon such termination, except for any rights any party may have in respect of
any breach by any other party of its or his obligations hereunder, none of the
parties hereto shall have any further obligation or liability hereunder.

        Section 8. Miscellaneous.

        (a)     This Agreement shall be binding upon and inure to the benefit of
the parties hereto and their Permitted Affiliate Transferees. Each of the
Stockholders hereby agrees that prior to any Transfer of any Shares to a
Permitted Affiliate Transferee, such Permitted Affiliate Transferee shall
execute a counterpart of this Agreement agreeing to be bound by the provisions
of this Agreement. No Transfer to a Permitted Affiliate Transferee shall be
effective unless such Permitted Affiliate Transferee has executed such
counterpart of this Agreement. Except as set forth above with respect to
Transfers to Permitted Affiliate Transferees, nothing in this Agreement shall
prohibit the Transfer of Shares by any of the Stockholders.

        (b)     Each of the parties hereto acknowledges and agrees that, in the
event of any breach of this Agreement, the non-breaching parties would be
irreparably harmed and could not be made whole by monetary damages. Accordingly,
each of the parties hereto agrees that the other parties, in addition to any
other remedy to which they may be entitled at law or in equity, shall be
entitled to compel performance of this Agreement pursuant to Section 8(m).

        (c)     The headings in this Agreement are for convenience only and
shall not be considered a part of or affect the construction or interpretation
of any provision of this Agreement.

        (d)     All notices, requests, demands and other communications
hereunder shall be in writing and shall be deemed to have been duly given if
delivered by same day or next day (or equivalent with respect to delivery
outside the United States) courier (guaranteed delivery) or telex or facsimile
(i) if to a Stockholder, at such Stockholder's address appearing on Schedule I
hereto or at any other address that such Stockholder may have provided in
writing to VoiceStream Holdings and the other Stockholders then party to this
Agreement and (ii) if to VoiceStream Holdings, at 3650 131st Avenue SE,
Bellevue, Washington 98006, U.S.A., Tel: 425-586-8014, Fax: 425-586-8080;
Attention: Alan R. Bender, Esq. or such other address as VoiceStream Holdings
may have furnished to the Stockholders in writing, with a copy (which shall not
constitute notice) to Friedman Kaplan & Seiler LLP, 875 Third Avenue, New York,
NY 10022, USA, Tel: 212-833-1107, Fax: 212-355-6401, Attention: Barry A.
Adelman, Esq. If a notice hereunder is transmitted by confirmed fax so as to
arrive during normal business hours during a Business Day at the place of
receipt, then such notice shall be deemed to have been given on such Business
Day at the place of receipt or, if so transmitted to arrive after normal
business hours during a Business Day at the place of receipt, then such notice
shall be deemed to have been given on the following Business Day at the place of
receipt. If such notice is sent by next-day courier or equivalent, it shall be
deemed to have been given on the third Business Day at the place of receipt
following sending provided, that the date of sending shall be deemed to be the
date at the place of receipt at the time such notice is posted.

                                       11
<PAGE>   12
        (e)     The provisions of this Agreement shall apply, to the full extent
set forth herein with respect to the Shares now or hereinafter owned by each
Stockholder (and its Permitted Affiliate Transferees), to any and all securities
of VoiceStream Holdings or any successor or assign of VoiceStream Holdings
(whether by merger, consolidation or otherwise) that may be issued in respect
of, in exchange for, or in substitution of such Shares, and shall be
appropriately adjusted for any stock dividends, stock splits, reverse splits,
combinations, recapitalizations and similar events occurring after the date
hereof.

        (f)     Copies of this Agreement will be available for inspection or
copying by any interested Person at the offices of VoiceStream Holdings through
the Secretary of VoiceStream Holdings. VoiceStream Holdings will otherwise take
all actions as may be necessary or appropriate to comply with any applicable law
relating to the validity and enforceability of shareholders agreements
containing the provisions of this Agreement.

        (g)     Except as expressly provided otherwise herein, neither this
Agreement nor any provision hereof may be changed, waived, discharged or
terminated orally, but only by an instrument in writing signed by VoiceStream
Holdings and each of the Stockholders. The failure of any party hereto to give
notice of the breach or non-fulfillment of any term or condition of this
Agreement shall not constitute a waiver thereof, nor shall the waiver of any
breach or non-fulfillment of any term or condition of this Agreement constitute
a waiver of any other breach or non-fulfillment of that term or condition or any
other term or condition of this Agreement.

        (h)     This Agreement may be amended or modified at any time by a
writing setting forth such amendment or modification, signed by VoiceStream
Holdings and by Stockholders (or their Permitted Affiliate Transferees) owning
in the aggregate at least 90% of the Shares owned by the Stockholders (and their
Permitted Affiliate Transferees); provided, however, that, unless such amendment
is signed by VoiceStream Holdings and by each Stockholder (or its Permitted
Affiliate Transferees) adversely affected by such amendment, no such amendment
or modification shall eliminate any right of any Stockholder (or its Permitted
Affiliate Transferees) or, in the case of the Omnipoint Designees, the Old
Omnipoint Board, to designate the member or members of the Board it is entitled
to designate in accordance with Section 3 hereof (it being understood and agreed
that this clause shall not prohibit the enlargement of the Board).

        (i)     This Agreement may be executed in any number of counterparts,
each of which shall be deemed an original, and all of which together shall be
considered one and the same agreement.

        (j)     The obligations of each of the Stockholders under this Agreement
shall be several with respect to each such Stockholder.

        (k)     This Agreement constitutes the entire understanding of the
parties hereto with respect to this subject matter hereof and supersedes all
prior understandings among such parties with respect to such subject matter.

                                       12
<PAGE>   13
        (l)     The validity of this Agreement, its construction, interpretation
and enforcement, and the rights of the parties hereunder, shall be determined
under, governed by and construed in accordance with the internal laws of the
State of New York applicable to contracts formed and performed entirely in such
state. Each party hereto agrees that, subject to Section 8(m) hereof, any suit,
action or other proceeding arising out of this Agreement shall be brought and
litigated in the courts of the State of Washington or the United States District
Court for the Western District of Washington and each party hereto hereby
irrevocably consents to personal jurisdiction and venue in any such court and
hereby waives any claim it may have that such court is an inconvenient forum for
the purposes of any such suit, action or other proceeding.

        (m)     Any and all disputes, controversies or claims (each a "Dispute")
between the Stockholders relating to the interpretation or enforcement or
performance of this Agreement shall be resolved by binding arbitration by the
American Arbitration Association in accordance with its rules, subject to the
following provisions:

                (i)     There shall be three arbitrators (the "Arbitrators")
which shall be appointed in accordance with the procedure of the American
Arbitration Association.

                (ii)    The expenses of the arbitration shall be borne equally
by the Stockholders involved in the arbitration, and each party shall bear its
own legal fees and expenses; provided, however, that the Arbitrators shall have
discretion to require that one party pay all or a portion of the expenses of
arbitration or the other party's legal fees and expenses in connection with any
particular arbitration.

                (iii)   The Arbitrators shall determine whether and to what
extent any party shall be entitled to damages or equitable relief. No party
shall be entitled to punitive damages or consequential damages or shall be
required to post a bond in connection with equitable relief.

                (iv)    The Arbitrators shall not have the power to add to nor
modify any of the terms or conditions of this Agreement. The Arbitrators'
decision shall not go beyond what is necessary for the interpretation and
application of the provisions of this Agreement in respect of the issue before
the Arbitrators. The Arbitrators' decision and award or permitted remedy, if
any, shall be based upon the issue as drafted and submitted by the respective
parties and the relevant and competent evidence adduced at the hearing(s).

                (v)     The Arbitrators shall have the authority to award any
remedy or relief provided for in this Agreement, in addition to any other remedy
or relief (including provisional remedies and relief) that a court of competent
jurisdiction could order or grant (but subject to the remedial limitations,
elsewhere set forth in this Agreement, including, but without limitation, the
aforesaid prohibition against punitive and consequential damages). The
Arbitrators written decision shall be rendered within sixty (60) days of the
hearing. The decision reached by the Arbitrators shall be final and binding upon
the parties as to the matter in dispute. To the extent that the relief or


                                       13
<PAGE>   14
remedy granted by the Arbitration is relief or remedy on which a court could
enter judgment, a judgment upon the award rendered by the Arbitrators may be
entered in any court having jurisdiction thereof (unless in the case of an award
of damages, the full amount of the award is paid within ten (10) days of its
determination by the Arbitrators). Otherwise, the award shall be binding on the
parties in connection with their continuing performance of this Agreement and in
any subsequent arbitral or judicial proceeding between the parties.

                (vi)    The arbitration shall take place in Seattle, Washington,
unless otherwise agreed by the parties, and shall be conducted in the English
language.

                (vii)   The arbitration proceeding and all filing, testimony,
documents and information relating to or presented during the arbitration
proceeding shall be disclosed exclusively for the purpose of facilitating the
arbitration process and for no other purpose.

                (viii)  The parties shall continue performing their respective
obligations under this Agreement notwithstanding the existence of a Dispute
while the Dispute is being resolved unless and until such obligations are
terminated, expire or are suspended in accordance with the provisions hereof.

                (ix)    The Arbitrators may, in their sole discretion, order a
pre-hearing exchange of information including production of documents, exchange
of summaries of testimony or exchange of statements of position, and shall
schedule promptly all discovery and other procedural steps and otherwise assume
case management initiative and control to effect an efficient and expeditious
resolution of the Dispute. At any oral hearing of evidence in connection with an
arbitration proceeding, each party and its counsel shall have the right to
examine its witnesses and to cross-examine the witnesses of the other party. No
testimony of any witness shall be presented in written form unless the opposing
party or parties shall have the opportunity to cross-examine such witness,
except as the parties otherwise agree in writing.

                (x)     Notwithstanding the dispute resolution procedures
contained in this Section 8(m), either party may apply to any court having
jurisdiction (a) to enforce this Agreement to arbitrate, (b) to seek provisional
injunctive relief so as to maintain the status quo until the arbitration award
is rendered or the Dispute is otherwise resolved, or (c) to challenge or vacate
any final judgment, award or decision of the Arbitrators that does not comport
with the express provisions of this Section 8(m).

        (n)     The failure of any party to seek redress for violation of, or to
insist upon the strict performance of , any provision of this Agreement shall
not prevent a subsequent act, which would have originally constituted a
violation, from having the effect of an original violation.

        (o)     The rights and remedies provided by this Agreement are
cumulative and the use of any one right or remedy by any party shall not
preclude or waive its right to use any or all other


                                       14
<PAGE>   15
remedies except as otherwise expressly provided in this Agreement. Such rights
and remedies are given in addition to any other rights the parties may have by
law, statute, ordinance or otherwise.

        (p)     The invalidity or unenforceability of any particular provision
of this Agreement shall not affect the other provisions hereof, and this
Agreement shall be construed in all respects as if such invalid or unenforceable
provision were omitted.

                                       15
<PAGE>   16
        IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of the day and year first above written.

VOICESTREAM WIRELESS HOLDING CORPORATION


By:  /s/ John W. Stanton
     ------------------------------------------------
     Name: John W. Stanton
     Title: Chairman and Chief Executive Officer


STOCKHOLDERS:


/s/ John W. Stanton
-----------------------------------------------------
John W. Stanton


/s/ Theresa E. Gillespie
-----------------------------------------------------
Theresa E. Gillespie


PN Cellular, Inc.


By:   /s/ Theresa E. Gillespie
     ------------------------------------------------
     Name: Theresa E. Gillespie
     Title: Treasurer


Stanton Family Trust


By:   /s/ Theresa E. Gillespie
     ------------------------------------------------
     Name: Theresa E. Gillespie, Trustee


Stanton Communications Corporation


By:   /s/ Theresa E. Gillespie
     ------------------------------------------------
     Name: Theresa E. Gillespie
     Title: Treasurer

<PAGE>   17
GS Capital Partners, L.P.


By:  GS Advisors L.L.C., General Partner


     By:  /s/ John E. Bowman
     ------------------------------------------------
     Name: John E. Bowman
     Title: Vice President


The Goldman Sachs Group, Inc.


By:  /s/ Terence M. O'Toole
     ------------------------------------------------
     Name: Terence M. O'Toole
     Title: Attorney-in-Fact


Bridge Street Fund 1992, L.P.


By:  Stone Street 1992 L.L.C., Managing General Partner


     By:  /s/ John E. Bowman
     ------------------------------------------------
     Name: John E. Bowman
     Title: Vice President


Stone Street Fund 1992, L.P.


By:  Stone Street 1992 L.L.C., General Partner


     By:  /s/ John E. Bowman
     ------------------------------------------------
     Name: John E. Bowman
     Title: Vice President

<PAGE>   18
Hutchison Telecommunications Holdings (USA) Limited


By:   /s/ Canning Fok
     ------------------------------------------------
     Name: Canning Fok
     Title: Director


Hutchison Telecommunications PCS (USA) Limited


By:   /s/ Susan Chow
     ------------------------------------------------
     Name: Susan Chow
     Title: Director

<PAGE>   19
ALLEN & COMPANY INCORPORATED


By:   /s/ Richard L. Fields
     ------------------------------------------------
     Name: Richard L. Fields
     Title: Manager


MADISON DEARBORN CAPITAL
  PARTNERS, L.P.

By:  Madison Dearborn Partners, L.P.,
     its General Partner

     By:  Madison Dearborn Partners, Inc.
          its General Partner


By:   /s/ James N. Perry
     ------------------------------------------------
     Name: James N. Perry
     Title: Manager


/s/ James N. Perry
-----------------------------------------------------
James N. Perry, Jr.


/s/ Richard L. Fields
-----------------------------------------------------
Richard L. Fields

<PAGE>   20
AVANCE CAPITAL


By:  /s/ Douglas G. Smith
     ------------------------------------------------
     Name:  Douglas G. Smith
     Title:  Sole Proprietor

AVANCE CAPITAL II


By:  /s/ Douglas G. Smith
     ------------------------------------------------
     Name:  Douglas G. Smith
     Title:  Sole Proprietor

AVANCE CAPITAL III


By:  /s/ Douglas G. Smith
     ------------------------------------------------
     Name:  Douglas G. Smith
     Title:  Sole Proprietor

DOUGLAS AND GABRIELA SMITH
1995 FAMILY TRUST


By:   /s/ Gabriela Smith
     ------------------------------------------------
     Name:  Gabriela Smith
     Title: Trustee



/s/ Douglas G. Smith
-----------------------------------------------------
Douglas G. Smith

<PAGE>   21
/s/ James J. Ross
-----------------------------------------------------
James J. Ross


ELIZABETH G. ROSS U/T/A, DATED MARCH 4, 1994


By:  /s/ James J. Ross
     ------------------------------------------------
     Name:  James J. Ross
     Title: Trustee


DAVID G. ROSS U/T/A, DATED JUNE 18, 1997


By:  /s/ James J. Ross
     ------------------------------------------------
     Name:  James J. Ross
     Title: Trustee

<PAGE>   22
SONERA CORPORATION


By:  /s/ Olli T. Tuohimaa
     ------------------------------------------------
     Name: Olli T. Touhimaa
     Title: Attorney in Fact

SONERA HOLDING, B.V.


By:  /s/ Olli T. Tuohimaa
     ------------------------------------------------
     Name: Olli T. Touhimaa
     Title: Attorney in Fact


<PAGE>   23
                                   SCHEDULE I

                                  STOCKHOLDERS

--------------------------------------------------------------------------------
       NAME AND ADDRESS OF STOCKHOLDER                      NUMBER OF SHARES
--------------------------------------------------------------------------------
John W. Stanton and Theresa E. Gillespie                       2,930,136
c/o VoiceStream Wireless Corporation
3650 131st Avenue S.E., Suite 400
Bellevue, WA 98006
Attention:  John W. Stanton
Fax: 425-586-8010
--------------------------------------------------------------------------------
PN Cellular, Inc.                                               1,686,069
c/o VoiceStream Wireless Corporation
3650 131st Avenue S.E., Suite 400
Bellevue, WA 98006
Attention:  John W. Stanton
Fax: 425-586-8010
--------------------------------------------------------------------------------
Stanton Family Trust                                              164,437
c/o VoiceStream Wireless Corporation
3650 131st Avenue S.E., Suite 400
Bellevue, WA 98006
Attention:  John W. Stanton
Fax: 425-586-8010
--------------------------------------------------------------------------------
Stanton Communications Corporation                              1,274,520
c/o VoiceStream Wireless Corporation
3650 131st Avenue S.E., Suite 400
Bellevue, WA 98006
Attention:  John W. Stanton
Fax: 425-586-8010
--------------------------------------------------------------------------------
GS Capital Partners, L.P.                                       8,986,738
c/o Goldman, Sachs & Co.
85 Broad Street
New York, NY 10004
Attention:  Terence O'Toole
Fax: 212-902-3000
--------------------------------------------------------------------------------

<PAGE>   24
--------------------------------------------------------------------------------
The Goldman Sachs Group, Inc.                                        68,821
c/o Goldman, Sachs & Co.
85 Broad Street
New York, NY 10004
Attention:  Terence O'Toole
Fax: 212-902-3000
--------------------------------------------------------------------------------
Bridge Street Fund 1992, L.P.                                       273,069
c/o Goldman, Sachs & Co.
85 Broad Street
New York, NY 10004
Attention:  Terence O'Toole
Fax: 212-902-3000
--------------------------------------------------------------------------------
Stone Street Fund 1992, L.P.                                        470,401
c/o Goldman, Sachs & Co.
85 Broad Street
New York, NY 10004
Attention:  Terence O'Toole
Fax: 212-902-3000
--------------------------------------------------------------------------------
Hutchison Telecommunications PCS (USA) Limited                   52,010,364
                                                      (Which includes 26,227,586
c/o Offshore Incorporations Limited                       shares of Common Stock
P.O. Box 957                                            issuable upon conversion
Offshore Incorporations Centre                 of the Company's 2.5% Convertible
Road Town, Tortola                                              Preferred Stock)
British Virgin Islands
Telephone No.: 809-494-2233
Facsimile No.: 809-494-4885

and:

c/o Hutchison Telecommunications Limited
22nd Floor, Hutchison House
10 Harcourt Road
Hong Kong
Attention: Ms. Edith Shih
Fax: 852-2128-1778
--------------------------------------------------------------------------------

<PAGE>   25
--------------------------------------------------------------------------------
Hutchison Telecommunications Holdings (USA) Limited             3,888,888

c/o Offshore Incorporations Limited
P.O. Box 957
Offshore Incorporations Centre
Road Town, Tortola
British Virgin Islands
Telephone No.: 809-494-2233
Facsimile No.: 809-494-4885

and:

c/o Hutchison Telecommunications Limited
22nd Floor, Hutchison House
10 Harcourt Road
Hong Kong
Attention: Ms. Edith Shih
Fax: 852-2128-1778
--------------------------------------------------------------------------------
Douglas G. Smith                                                1,196,398
6200 Brookside Drive
Chevy Chase, MD 20815
--------------------------------------------------------------------------------
Avance Capital                                                  2,220,266
Attn: Douglas G. Smith
6200 Brookside Drive
Chevy Chase, MD 20815
--------------------------------------------------------------------------------
Avance Capital II                                                 750,000
Attn: Douglas G. Smith
6200 Brookside Drive
Chevy Chase, MD 20815
--------------------------------------------------------------------------------
Avance Capital III                                                375,000
Attn: Douglas G. Smith
6200 Brookside Drive
Chevy Chase, MD 20815
--------------------------------------------------------------------------------
Douglas & Gabriela Smith                                          519,482
1995 Family Trust
Attn: Gabriela Smith, Trustee
6200 Brookside Drive
Chevy Chase, MD 20815
--------------------------------------------------------------------------------

<PAGE>   26
--------------------------------------------------------------------------------
Richard L. Fields                                                 317,368
75 Central Park South, Apt. 15B
New York, NY 10022
--------------------------------------------------------------------------------
Allen & Company Incorporated                                    2,290,522
c/o Richard L. Fields, Managing Director
711 Fifth Avenue
New York, NY 10022
--------------------------------------------------------------------------------
James N. Perry, Jr.                                                50,874
Madison Dearborn Capital Partners, LP
Three First National Plaza, Suite 1330
Chicago, IL 60602
--------------------------------------------------------------------------------
Madison Dearborn Capital Partners, LP                           3,232,149
c/o James N. Perry, Jr., Managing Director
Three First National Plaza, Suite 1330
Chicago, IL 60602
--------------------------------------------------------------------------------
James J. Ross                                                     582,445
c/o Becker Ross Stone DeStefano & Klein
317 Madison Avenue, Suite 1410
New York, NY 10017
--------------------------------------------------------------------------------
James J. Ross, as Trustee, of Elizabeth G. Ross   An Aggregate of 145,950
U/T/A, dated March 4, 1994
c/o Becker Ross Stone DeStefano & Klein
317 Madison Avenue, Suite 1410
New York, NY 10017

James J. Ross, as Trustee, of David G. Ross
U/T/A, dated June 18, 1997
c/o Becker Ross Stone DeStefano & Klein
317 Madison Avenue, Suite 1410
New York, NY 10017
--------------------------------------------------------------------------------
Sonera Corporation
P.O. Box 106
FIN-00051-TELE
Teollisuuskatu 15, Helsinki
Attn: Kaj-Erik Relander, Executive Vice President
Facsimile: 011 358 2040 3770
--------------------------------------------------------------------------------

<PAGE>   27
--------------------------------------------------------------------------------
Sonera Holding, B.V.                                            8,792,555
c/o Sonera Corporation
P.O. Box 106
FIN-00051-TELE
Teollisuuskatu 15, Helsinki
Attn: Kaj-Erik Relander, Executive Vice President
Facsimile: 011 358 2040 3770
--------------------------------------------------------------------------------
Upon the execution and delivery of the attached agreement, the following
Stockholder shall become a party to this Agreement.
--------------------------------------------------------------------------------
Telephone and Data Systems, Inc.               [Number of Shares shall be as set
30 North LaSalle, Suite 4000                   forth on the agreement attached
Chicago, IL 60602                              hereto as Exhibit A.]
Attention: LeRoy T. Carlson, Jr., President
Facsimile: 312-630-9299
--------------------------------------------------------------------------------
<PAGE>   28
                                                                    Exhibit A to
                                                                Voting Agreement

                                    AGREEMENT

        AGREEMENT, dated as of __________, 2000, by and between VOICESTREAM
WIRELESS CORPORATION (f/k/a VoiceStream Wireless Holding Corporation), a
Delaware corporation ("VoiceStream"), and TELEPHONE AND DATA SYSTEMS, INC., a
Delaware corporation ("TDS");

        WHEREAS, VoiceStream has entered into a Voting Agreement ("Voting
Agreement") dated as of February 25, 2000, together with certain stockholders of
VoiceStream set forth on Schedule I thereof ("Stockholders");

        WHEREAS, all capitalized terms used herein and not otherwise defined
shall have the meanings set forth in the Voting Agreement;

        WHEREAS, in the Voting Agreement, the Stockholders and VoiceStream have
agreed that, at the time of the closing of the Aerial Reorganization, TDS and
VoiceStream shall execute and deliver this Agreement to evidence the admission
of TDS as a party to the Voting Agreement;

        WHEREAS, the Aerial Reorganization is being consummated concurrently
with the execution of this Agreement;

         NOW, THEREFORE, in consideration of the foregoing and the mutual
covenants and agreements set forth herein, the parties hereto agree as follows:

        1.      TDS hereby accepts and agrees to all of the terms and conditions
                of the Voting Agreement and agrees to become a party to the
                Voting Agreement as a Stockholder effective immediately.

        2.      The Voting Agreement shall not in any way limit, amend or modify
                any of the terms or provisions of the Investor Agreement dated
                the date hereof among TDS, VS Washington Corporation and
                VoiceStream.

        3.      VoiceStream, by action of its Board of Directors, shall appoint
                a Qualified TDS Designee to the Board of Directors of
                VoiceStream on the later of (i) the date hereof or (ii) promptly
                after TDS designates a Qualified TDS Designee.

        4.      This Agreement shall become effective as of the Effective Time
                of the Aerial Reorganization and shall supersede the Parent
                Stockholder Agreement, dated as of September 17, 1999, among
                Aerial, TDS, VoiceStream and VS Washington

<PAGE>   29
                Corporation (f/k/a VoiceStream Wireless Corporation) and the
                individuals and entities set forth on Schedule I thereto, which
                shall terminate by its terms at such time.

        5.      The number of Shares Beneficially Owned by TDS as of the date of
                this Agreement is _______ Shares.

                IN WITNESS WHEREOF, the parties hereto have caused this
Agreement to be duly executed as of the day and year first above written.


                               VOICESTREAM WIRELESS CORPORATION


                               By:
                                   ---------------------------------------------
                               Name:
                               Title:

                               TELEPHONE AND DATA SYSTEMS, INC.


                               By:
                                   ---------------------------------------------
                               Name:
                               Title: