<PAGE>   1
                                                                   EXHIBIT 10.16


                                                                   June 20, 2001



Mohan Gyani
c/o AT&T Wireless Services, Inc.
7277 164th Avenue NE
Redmond, WA  98052

Dear Mohan:

         It gives me great pleasure to confirm the terms and conditions of your
employment as President & Chief Executive Officer of AT&T Mobility Services for
AT&T Wireless Services, Inc. ("AT&T Wireless" or the "Company"). In addition,
this agreement will detail the terms and conditions of your employment and
outline the current major features of AT&T Wireless' compensation and benefit
plans and practices. This agreement will amend, restate and supersede your
letter agreement with AT&T Corp. dated January 15, 2000, as supplemented by the
addenda dated as of March 9, 2000 and as of May 1, 2001. The effective date of
this agreement is the date of the consummation of the split-off of the Company
from AT&T Corp. (the "Effective Date").

DUTIES

         As President & Chief Executive Officer of AT&T Mobility Services for
AT&T Wireless, you will report to, and only to, the Company's CEO (currently
John Zeglis). Your principal office location will be in San Francisco,
California, but you will have a second office in Redmond, Washington. The
Company will bear all reasonable expenses for your travel to and stay in
Redmond, Washington. You will travel to Redmond as requested by the Company's
CEO.

BASE SALARY

         Your initial base salary will be $700,000 per year. Currently, this
rate is reviewed annually for increase to reflect individual performance and
base salary structure changes applicable to comparable executives; provided,
however, that your base salary will in no event be reduced at any time.

SPECIAL PAYMENT

         The Company will provide you with a special incentive payment of
$600,000, less applicable withholding taxes, in acknowledgment of the scope and
responsibility associated with your position. Of this amount, $500,000 will be
paid on the Effective Date and $100,000 will be paid on January 15, 2002 or
earlier upon your death, "Long Term
<PAGE>   2
Disability," termination by the Company without "Cause," or termination by you
for "Good Reason" (as each of those terms is defined in this agreement).

ANNUAL BONUS

         The annual bonus for comparable executives is currently based on
measures of Company, unit, and individual performance and is paid in cash. The
2001 target (not actual) annual bonus for your position is 100% of your base
salary or $700,000.

LONG TERM INCENTIVES

         STOCK OPTIONS

         Promptly after the later of the Effective Date and the consummation of
the split-off of the Company from AT&T Corp. (the "Grant Date"), subject to
action by the Compensation Committee of the Company's Board of Directors, you
will be awarded an option under the Company's 2001 Long Term Incentive Plan (the
"2001 Plan"), which will be covered by a Form S-8 registration statement, to
purchase 360,000 shares of AT&T Wireless common stock at an option price equal
to the fair market value (defined as the average of the opening and closing
stock prices on the NYSE) on the Grant Date. The option will be subject to the
terms and conditions of the 2001 Plan and a stock option award agreement,
including but not limited to the following: assuming continued employment, the
option will vest 1/3 on October 28, 2001, 1/3 on February 14, 2002 and 1/3 on
February 14, 2003. In addition:

         (A) In the event that, prior to January 31, 2004, the closing stock
price of AT&T Corp. common stock is equal to or greater than $58 for ten
consecutive trading days (the "Collar Date"), the option will immediately vest
and, effective six months and one day from the Collar Date, the option will be
canceled.

         (B) Subject to (A) above, the option shall be subject to your rights
under the "Severance Benefit" section of this agreement with regard to
"Outstanding Stock Options."

         (C) The option shall not be subject to any clawback, forfeiture or
similar provision that is any more constraining of you than as applied to the
options granted to you at the time of your hire.

         As with the Annual Bonus, stock option grants are closely linked with
the Company's strategy to meet the challenges of an ever-changing marketplace.
Accordingly, the Company cannot guarantee continuation of stock option grants in
the current format, nor can it guarantee annual grant levels to individual
participants.

         RESTRICTED STOCK UNITS

         On the Grant Date, and subject to action by the Compensation Committee
of the Company's Board of Directors, you will be granted a restricted stock unit
award under the


                                       -2-
<PAGE>   3
2001 Plan for 200,000 shares of AT&T Wireless common stock. Such award is
subject to the terms and conditions of the 2001 Plan and a restricted stock unit
agreement, including but not limited to the following: assuming continued
employment, the restricted stock unit award will vest 1/3 on October 28, 2001,
1/3 on February 14, 2002 and 1/3 on February 14, 2003 or earlier on a Change in
Control or your death, Long Term Disability, termination of employment by the
Company without Cause or termination of employment by you for Good Reason. The
restricted stock units will not be subject to any clawback, forfeiture or
similar provision that is any more constraining of you than as applied to the
options granted to you at the time of your hire. Subject to adoption and
approval of an AT&T Wireless Deferred Compensation Plan, the restricted stock
units will be eligible for deferral into such plan.

DEFERRED COMPENSATION ACCOUNTS

         The Company has assumed the obligations of AT&T Corp. for a Deferred
Compensation Account established in your name in connection with the January 15,
2000 agreement with a balance of $6,000,000 (the "DCA1") and on the Effective
Date will establish another Deferred Compensation Account in your name with a
balance of $3,500,000 (the "DCA2"). The Deferred Compensation Accounts (each a
"DCA") will be maintained and paid to you in accordance with the provisions set
forth below. Each DCA will be maintained as a bookkeeping account on the records
of the Company, and you will have no ownership interest in either DCA, nor in
any assets of the Company with respect thereto. Neither DCA may be assigned,
pledged or otherwise alienated by you, and any attempt to do so, or any
garnishment, execution or levy of any kind with respect to either DCA, will not
be recognized. You will not have any right to receive any payment with respect
to either DCA, except as expressly provided below. The DCA1 and the DCA 2 will
be credited with interest from January 16, 2000 and May 1, 2001, respectively,
as described below.

         Payments from the DCAs are in addition to and not in lieu (nor will
they or anything in this agreement postpone, reduce or negate impact) of
qualified or non-qualified pension, savings or other retirement plan, program or
arrangement covering you or any amounts due you under this agreement, including
but not limited to amounts and benefits due as a result of a future termination.
The DCA payments provided under this agreement are subject to payroll tax
withholding and reporting, and amounts credited to the DCAs are not included in
the base for calculating benefits (nor will such amounts offset any benefits)
under any employee or management benefit plan, program or practice.

           DCA1

         The interest credited on the amounts in the DCA1 will be compounded as
of the end of each calendar quarter for as long as any sums remain in the DCA1,
and the quarterly rate of interest applied at the end of any calendar quarter
will be equal to one-quarter of the sum of (1) the average 30-year Treasury Note
rate for the previous quarter plus (2) 2% percent.


                                       -3-
<PAGE>   4
         The amounts credited to the DCA1, including interest, will be paid in
five approximately equal annual installments beginning in the quarter following
your retirement, provided your retirement is after age 55. Should you die prior
to the time that the entire sum in the DCA1 has been paid to you, the Company
will make the remaining payments described above in this paragraph to your
beneficiary designated on a Company form filed with Executive Human Resources,
or to your estate if no beneficiary has been designated. The Company, at your
request, will consider in good faith exchanging all or part of the DCA1 for an
enhanced estate program.

         In the event of your termination of employment prior to age 55 for any
reason, including, but not limited to, a voluntary termination, all amounts
credited to the DCA1 through the last day of the first calendar quarter of the
calendar year following the year in which such termination of employment occurs
will be paid to you (or your designated beneficiary or estate, as described
above, in the event of your death) within 30 business days after the end of such
quarter.

         DCA2

         The interest credited on the amounts in the DCA2 will be compounded as
of the end of each calendar quarter for as long as any sums remain in the DCA2,
and the quarterly rate of interest applied at the end of any calendar quarter
will be equal to one-quarter of the sum of (1) the average 10-year Treasury Note
rate for the previous quarter plus (2) 0.50% percent.

         The DCA2 will vest (1) $2,500,000 on August 1, 2001, and (2) $1,000,000
on February 14, 2002 (including interest thereon), contingent upon your
continued employment with the Company through the vesting dates, provided that
the DCA2 will fully vest on a Change in Control, your termination of employment
as a result of your death or Long Term Disability or, subject to the other
provisions of this agreement, a termination by the Company not for Cause or by
you for Good Reason. As of the vesting dates, you will be responsible for
applicable FICA and Medicare taxes on the amount vested on such date. The unpaid
balance in the DCA2 will continue to accrue interest at the rate of return set
forth above until it is paid out in its entirety as indicated below.

         The vested amounts credited to the DCA2, including interest, will be
paid in five approximately equal annual installments beginning in the quarter
following retirement, provided your retirement is at or after age 55. Should you
die prior to the time that the entire sum in the DCA2 has been paid to you, the
Company will make the remaining payments described above in this paragraph to
your beneficiary designated on a Company form filed with Executive Human
Resources, or to your estate if no beneficiary has been designated.

         Notwithstanding the foregoing, in the event of your termination of
employment after February 14, 2002 but prior to age 55 for any reason,
including, but not limited to, a voluntary termination, all amounts credited to
the DCA2 through the last day of the first calendar quarter of the calendar year
following the year in which such termination of


                                       -4-
<PAGE>   5
employment occurs will be paid to you (or your designated beneficiary, or
estate, as described above, in the event of your death) within 30 business days
after the end of such quarter.

         In the event that prior to February 14, 2002 and before a Change in
Control (i) you terminate your employment voluntarily for Good Reason or (ii)
the Company terminates your employment for other than Cause, which in either
case entitles you to the benefits under the Severance Benefit section (A) of
this agreement (which will be paid in either such case except as provided in
this paragraph), $1,000,000 will be forfeited from the DCA2 and your remaining
DCA2 balance (including interest thereon) will be paid to you (or to your
beneficiary or estate, in the event of your death) in a lump sum as soon as is
practical in the calendar quarter following the applicable termination. In the
event the Company determines that there is Cause for termination of employment,
the Company will provide you with written notice specifying the grounds upon
which its determination is based.

SEVERANCE BENEFIT

         (A) In the event of any Company-initiated termination, including
termination by you for Good Reason, other than for death, Long Term Disability
or Cause, you will be entitled to the following:

         1.       A "Severance Payment" equal to 200% of the sum of your annual
                  base salary and "target" annual bonus in effect on the date of
                  such termination, payable in the month following the month of
                  termination.

         2.       Annual Bonus: To the extent all or a portion of your annual
                  bonus for the current year and/or prior year has not been
                  paid, the Company will pay an amount equal to the target
                  annual bonus prorated for the total period of eligibility
                  based on a formula, the numerator of which is equal to the
                  number of days in the applicable calendar year for which the
                  annual bonus is being paid (up to and including the date of
                  termination), and the denominator of which is 365 and payable
                  to you within 20 business days after such termination;
                  provided that if the annual bonus for the prior year had been
                  declared before your termination and is higher than the target
                  bonus, it will be paid in lieu of the target bonus for the
                  prior year.

         3.       Annual Long Term Incentive Awards:

                  -        Outstanding performance shares and restricted stock
                           units, including those granted upon your hire, are
                           retained and distributed at the end of each
                           three-year cycle. Dividend equivalents continue to be
                           paid until all units are paid out.


                                       -5-
<PAGE>   6
                  -        Outstanding stock options, including those granted
                           upon your hire (including the awards granted in
                           connection with the Company's initial public offering
                           and the awards granted as hiring incentives), are
                           retained and immediately fully vest, with the full
                           remaining term under the original terms and
                           conditions of the grants to exercise.

         4.       Deferred Compensation Accounts:

                  -        Any outstanding balance in either DCA will be paid
                           within 30 days from your termination date, except as
                           provided under "DCA2."

         5.       Medical Coverage:

                  -        You and your currently eligible dependents, for life,
                           will have access to AT&T Wireless medical benefits,
                           which to the extent not paid for by AT&T Wireless
                           under a program, will be made available to you on the
                           same basis as other similarly situated former
                           executives.

         6.       Special Payments:

                  -        Any outstanding payments will be paid within 30 days
                           from your termination date.

         7.       Other Amounts:

                  -        Any other amounts or benefits due under this
                           agreement or under any Company plan or program will
                           be as so provided.

         (B) In the event of your death or Long Term Disability, you will be
entitled to items under clauses (A)2, (A)3, (A)4 and (A)7 above.

         (C) The medical benefits under clause (A)5 above will also be made
available in the event of your voluntary resignation without Good Reason.

         (D) Upon termination of your employment for any reason or no reason
after the Effective Date (whether initiated by you or the Company), (1) all
stock options issued to you prior to the Effective Date will immediately and
fully vest and all such stock options (including those previously vested) will
remain exercisable until the expiration of their original stated term and (2)
outstanding performance shares and restricted stock units issued to you before
the Effective Date will be retained by you and distributed at the end of the
relevant three-year cycle with dividend equivalents to be paid until the units
are paid out.

         For purposes of this agreement:

         "Cause" means:


                                       -6-
<PAGE>   7
         (1)      Your conviction (including a plea of guilty or nolo
                  contendere) of a felony involving theft or moral turpitude or
                  relating to the business of the Company, other than a felony
                  predicated on your vicarious liability. Vicarious liability
                  means, and only means, any liability which is based on acts of
                  the Company for which you are charged solely as a result of
                  your offices with the Company and in which either (i) you were
                  not directly involved or did not have prior knowledge of such
                  actions or inactions, or (ii) counsel had advised that the
                  action or inaction was permissible.

         (2)      You engage in conduct that constitutes willful gross neglect
                  or willful gross misconduct in carrying out your duties under
                  this agreement, resulting, in either case, in material
                  economic harm to the Company and its subsidiaries and
                  divisions.

         "Good Reason" means any termination of your Company employment,
         initiated by you, resulting from any of the following events, without
         your express written consent, which are not cured by the Company within
         20 days of your giving the Company written notice thereof:

         (1)      A reduction in your base salary and target annual incentive to
                  less than $1,400,000 or the failure of the Company to provide
                  you with stock options, restricted stock units, and/or other
                  equity incentive awards available to AT&T Wireless executives
                  at a level comparable with your position.

         (2)      The assignment to you of any duties inconsistent with, or, any
                  substantial alteration in, your status or responsibilities
                  (other than as a result of your mental or physical incapacity)
                  as in effect immediately prior thereto,

         (3)      A change in your work location of more than 50 miles from the
                  work location as of the Effective Date.

         (4)      A change in your reporting relationship that differs from the
                  reporting relationship described in the section under Duties
                  hereof, provided; however that subject to your written
                  consent, you may be reassigned to an operating position or
                  status comparable to this position as of the Effective Date
                  reporting to a comparable officer.

         (5)      A diminution in title or a material diminution in duties,
                  authority or responsibilities.

         (6)      A material breach of any provisions hereof by the Company.


                                       -7-
<PAGE>   8
         (7)      Failure of the Compensation Committee of the Company's Board
                  of Directors to grant the stock option and restricted stock
                  units referred to above within 60 days after the Effective
                  Date.

                  You must notify the Company within 60 days following knowledge
         of an event you believe constitutes Good Reason, or such event will not
         constitute Good Reason hereunder. In the event the Good Reason event is
         clause (7) above, you will not be entitled to $500,000 of the amount
         described in the Special Payment section or to the DCA2.

                  All severance amounts will be paid without any obligations to
         mitigate or any offset for other amounts earned.

                  "Long Term Disability" means termination of your employment
         with the Company with eligibility to receive a disability
         benefit/allowance under any long term disability plan of the Company or
         any affiliate of the Company.

CHANGE IN CONTROL PROVISIONS

         (A) If within two years following a Change in Control (as defined in
         Attachment A), you become entitled to the benefits provided in Part (A)
         of the Severance Benefit section above, you will be entitled to 300%
         rather than 200% under clause (A)1.

         (B) Immediately following a Change in Control, all amounts and benefits
         to which you are entitled but not yet vested, whether under this
         agreement or otherwise, will become fully vested.

         (C) If, following a change in ownership within the meaning of Internal
         Revenue Code ("Code") Section 280G(b)(2)(A)(i)(I) or (II), the
         aggregate of all payments or benefits provided to you hereunder, and
         under any other plans or programs of the Company or any other payments
         in the nature of compensation within the meaning of Section 280G(b)(2)
         of the Code (the "Aggregate Payment") is determined to constitute a
         parachute payment within the meaning of Section 280G(b)(2) of the Code,
         the Company will pay you, prior to the time any excise tax imposed by
         Section 4999 of the Code ("Excise Tax") is payable with respect to such
         Aggregate Payment, an additional amount (the "Gross-Up Payment") which,
         after the imposition of all income, employment, excise and other taxes
         thereon, permits you to retain an amount equal to the Excise Tax on the
         Aggregate Payment. The determination of whether the Aggregate Payment
         constitutes a parachute payment and, if so, the amount to be paid to
         you and the time of payment pursuant to this Part (C) will be made by
         an independent auditor (the "Auditor") selected by the Company and
         reasonably acceptable to you and will be paid for by the Company. All
         fees and expenses of the Auditor will be borne solely by the Company.
         Any Gross-Up


                                       -8-
<PAGE>   9
         Payment will be paid by the Company to you within fifteen days of
         receipt of the Auditor's determination. Any determination by the
         Auditor will be binding upon the Company and you, except to the extent
         the next paragraph hereof applies.

         As a result of the uncertainty in the application of Sections 280G and
         4999 of the Code at the time of the initial determination by the
         Auditor hereunder, it is possible that the Gross-Up Payment made will
         have been an amount more than the Company should have paid pursuant to
         this Part C (the "Overpayment") or that the Gross-Up Payment made will
         have been an amount less than the Company should have paid pursuant to
         this Part C (the "Underpayment"). In the event that there is a final
         determination by the Internal Revenue Service, or a final determination
         by a court of competent jurisdiction, that an Overpayment has been
         made, any such Overpayment will be treated for all purposes as a loan
         to you which you will repay to the Company together with interest at
         the applicable federal rate provided for in Section 7872(f)(2) of the
         Code. In the event that there is a final determination by the Internal
         Revenue Service, or a final determination by a court of competent
         jurisdiction, that an Underpayment arises under this agreement, any
         such Underpayment will be promptly paid by the Company to or for the
         benefit of you, together with interest at the applicable federal rate
         provided for in Section 7872(f)(2) of the Code.

         You will notify the Company in writing of any claim by the IRS that, if
         successful, would result in an Underpayment and would require the
         payment by the Company of an additional Gross-Up Payment. Such
         notification will be given as soon as practicable but no later than ten
         business days after you are informed in writing of such claim and will
         apprise the Company of the nature of such claim and the date on which
         such claim is requested to be paid. You will not pay such claim prior
         to the expiration of the 30-day calendar period following the date on
         which you give such notice to the Company (or shorter period ending on
         the date that any payment of taxes with respect to such claim is due).
         If the Company notifies you in writing prior to the expiration of such
         period that it desires to contest such claim, you will:

                  (i)      give the Company any information reasonably requested
                           by the Company relating to such claim,

                  (ii)     take such action in connection with contesting such
                           claim as the Company will reasonably request in
                           writing from time to time, including, without
                           limitation, accepting legal representation with
                           respect to such claim by an attorney reasonably
                           selected by the Company,

                  (iii)    cooperate with the Company in good faith in order to
                           effectively contest such claim, and


                                       -9-
<PAGE>   10
                  (iv)     permit the Company to participate in any proceeding
                           relating to such claim; provided, however, that the
                           Company will bear and pay directly all costs and
                           expenses (including additional interest and
                           penalties) incurred in connection with such contest
                           and will indemnify and hold you harmless, on an
                           after-tax basis, for any Excise Tax or income or
                           employment tax (including interest and penalties with
                           respect thereto) imposed as a result of such
                           proceeding and payment of costs and expenses. Without
                           limitation on the foregoing provisions of this Part
                           (C), the Company will control all proceedings taken
                           in connection with such contest, provided that the
                           Company's control of the contest will be limited to
                           issues with respect to which a Gross-Up Payment would
                           be payable hereunder, and you will be entitled to
                           settle or contest, as the case may be, any other
                           issue raised by the Internal Revenue Service or any
                           other taxing authority.

                  In the event that the Company does not so timely notify you,
         fails to file necessary documents contesting the claim or it is
         necessary to pay such amounts while contesting such claims, the Company
         will promptly pay you the Gross-Up Payment.

BENEFITS: You will, of course, be eligible for the benefit programs currently
available to all AT&T Wireless executives at your level, and you will be
eligible for future compensation and benefit plans established for executives at
your level based on the then current eligibility requirements established for
participation in such future benefits. In addition, you will be entitled to five
weeks annual vacation.

OTHER PROVISIONS: It is agreed and understood that you will not disclose the
specific terms of this agreement or any fact concerning its negotiation or
implementation, except in compliance with process, prior to the information
being made public by the Company. You may, however, discuss the contents of this
agreement with your spouse, legal and/or financial counselor and the forfeiture
provisions to any potential future employer.

         (a) Competition. As indicated in the AT&T Non-Competition Guideline
         that was included as Attachment B to the January 15, 2000 agreement
         between you and AT&T Corp., a number of AT&T Corp. incentive
         arrangements and/or non-qualified benefits were subject to
         non-competition constraints that result in the forfeiture of future
         amounts, benefits or rights if such guidelines are violated. AT&T
         Wireless is considering adopting noncompetition guidelines that will
         apply to its equity grants and benefit plans (if adopted, the
         "Guidelines"). In no event will the Guidelines or any incentive
         arrangements or non-qualified benefits as they apply to you require you
         to agree to a prohibition as to certain activities as a condition of
         receiving (as opposed to the forfeiture if you violate the Guidelines),
         permit recapture of any amounts or benefits previously paid or provided
         to you or be broader than as currently set forth in the AT&T
         Non-Competition Guidelines as modified herein. Furthermore, the


                                      -10-
<PAGE>   11
         limitation in the Guidelines will in no event apply to the items
         referred to as Hiring Incentives in the January 15, 2000 agreement.
         This provision will override any provision in any plan, program or
         grant. You will also have the benefit of Section 5.7 of the Employee
         Benefits Agreement dated as of June 7, 2001 between AT&T Corp. and AT&T
         Wireless.

         The AT&T Non-Competition Guidelines, and hence the Guidelines, (and any
         "non-competition clause") will be modified as follows:

         (1)      Section 4 Subpart 2(c)(i) will be deemed violated only if the
                  violation is willful, with intent to damage, in a public forum
                  (i.e., lectures, to the media, in published materials, to
                  analysts or in comparable forums) and is of a material nature.

         (2)      Section 4 Subpart 2(c)(2) will only be violated if you,
                  directly or indirectly, (i) recruit, solicit, induce or
                  attempt to induce, or encourage others to recruit, solicit or
                  induce, any employee of AT&T Wireless or an affiliate of AT&T
                  Wireless to terminate their employment with AT&T Wireless or
                  any affiliate, to join an entity with which you are affiliated
                  or (ii) offer employment to any employee of AT&T Wireless;
                  provided that the foregoing will not be violated by the
                  general advertising for employees or the hiring of employees
                  by entities with which you are affiliated so long as you are
                  not involved, either directly or indirectly, in recruiting,
                  soliciting, inducing or attempting to induce, or in
                  encouraging others in the recruiting, soliciting or inducing
                  of, any employee to leave AT&T Wireless and join any entity
                  with which you are affiliated.

         (3)      Section 4 Subpart 2(a) will be modified by deleting "but will
                  not be limited to" and it will not be violated by your owning
                  less than 3% of the debt or equity of a publicly traded entity
                  or your investing in private equity funds, investment pools or
                  other similar vehicles so long as you own less than 5% of the
                  equity in the vehicle.

         (4)      The Guidelines will not be violated by any activity or action
                  more than two years after any termination of employment (one
                  year in the case of "establishing a relationship with"
                  limitation) or by establishment of a relationship with an
                  entity that becomes a "competitor of the Company" after you
                  established the relationship unless you were hired to assist
                  the entity in becoming a Competitor.

         (5)      Section 4 Subpart 2(b) will be modified so that it only
                  applies to significant and direct competitors (such as
                  currently MCI Worldcom, Sprint and any of the regional Bell
                  operating companies and major wireless companies such as
                  currently Bell Atlantic, Sprint PCS, SBC, Nextel, and Vodafone
                  Airtouch PLC).


                                      -11-
<PAGE>   12
         (6)      Notwithstanding anything in the Guidelines to the contrary, no
                  forfeiture or cancellation will take place unless AT&T
                  Wireless will have first given you written notice of its
                  intent to so forfeit, or cancel or pay out and you have not,
                  within 30 calendar days of giving of such notice to you,
                  ceased such unpermitted competitive activity, provided that
                  the foregoing prior notice procedure will not be required with
                  respect to a competitive activity which you instituted after
                  AT&T Wireless informed you in writing that it believed such
                  activity violated the Guidelines.

         (b)      Confidentiality.

                  You agree that you will not, at any time during your
         employment pursuant to this agreement or thereafter, disclose or use
         any trade secret, proprietary or confidential information of the
         Company or any subsidiary or affiliate of the Company, except as
         required in the course of such employment or with the written
         permission of the Company or, as applicable, any subsidiary or
         affiliate of the Company or as may be required by law; provided that,
         if you receive legal process with regard to disclosure of such
         information, you will promptly notify the Company and cooperate with
         the Company in seeking a protective order.

                  You agree that at the time of the termination of your
         employment with the Company, whether at the insistence of you or the
         Company, and regardless of the reasons therefor, you will deliver to
         the Company, and not keep or deliver to anyone else, any and all notes,
         files, memoranda, papers and, in general, any and all physical matter
         containing information, including any and all documents significant to
         the conduct of the business of the Company or any subsidiary or
         affiliate of the Company which are in your possession, except for any
         documents for which the Company or any subsidiary or affiliate of the
         Company has given written consent to removal at the time of the
         termination of your employment and your personal rolodex, phone book
         and similar items.

                  You agree that the Company's remedies at law would be
         inadequate in the event of a breach or threatened breach of this
         paragraph (b); accordingly, the Company will be entitled, in addition
         to its rights at law, to an injunction and other equitable relief
         without the need to post a bond.

INDEMNIFICATION

         The Company will indemnify and hold you harmless to the fullest extent
permitted by applicable law with regard to any action or inaction by you as an
officer or director of the Company or any affiliate or as a fiduciary of any
benefit plan of the Company or any affiliate both during and after your term of
employment. The Company will cover you under director and officer liability
insurance to the same extent it covers other officers and directors both during
and after the term of employment.


                                      -12-
<PAGE>   13
DISPUTE RESOLUTION

         At your option or the Company's, any dispute, controversy, or question
arising under, out of or relating to this agreement or the breach thereof, other
than that for injunctive relief under the above paragraph (b), will be referred
for decision by arbitration in the State of Washington by a neutral arbitrator
selected by the parties hereto. The proceeding will be governed by the Rules of
the American Arbitration Association then in effect or such rules last in effect
(in the event such Association is no longer in existence). If the parties are
unable to agree upon such a neutral arbitrator within 30 days after either party
has given the other written notice of the desire to submit the dispute,
controversy or question for decision as aforesaid, then either party may apply
to the American Arbitration Association for an appointment of a neutral
arbitrator, or if such Association is not then in existence or does not act in
the matter within 30 days of application, either party may apply to the
Presiding Judge of the Superior Court of any county in Washington for an
appointment of a neutral arbitrator to hear the parties and settle the dispute,
controversy or question, and such Judge is hereby authorized to make such
appointment. In the event that either party exercises the right to submit a
dispute arising hereunder to arbitration, the decision of the neutral arbitrator
will be final, conclusive and binding on all interested persons and no action at
law or equity will be instituted or, if instituted, further prosecuted by either
party other than to enforce the award of the neutral arbitrator. The award of
the neutral arbitrator may be entered in any court that has jurisdiction. In the
event that you are successful in pursuing any material claims or disputes
arising out of this agreement, the Company will pay all of your attorneys' fees
and costs reasonably incurred, including the compensation and expenses of any
arbitrator. In any other case, you and the Company will each bear all their own
costs and attorneys fees, except the Company will in all events pay the costs of
any arbitrator appointed hereunder.

CHOICE OF LAW

         The construction, interpretation and performance of this agreement will
be governed by the laws of the State of Delaware, without regard to its conflict
of laws rule.

ASSIGNMENT

         This agreement will inure to the benefit of and be binding upon the
Company and its successors and assigns, provided that the Company may not assign
this agreement except in connection with an assignment or disposition of all or
substantially all of the assets or stock of the Company, or by law as a result
of a merger or consolidation. In the event of such assignment, a failure by the
successor to specifically assume in writing, delivered to you, the obligations
and liabilities of the Company hereunder will be deemed a material breach of
this agreement.

         This agreement reflects the entire agreement regarding the terms and
conditions of your employment. Accordingly, it supersedes and completely
replaces any prior oral or written communication on this subject. This agreement
is not an employment contract and


                                      -13-
<PAGE>   14
should not be construed or interpreted as containing any guarantee of continued
employment. The employment relationship at AT&T Wireless or any of its
affiliates is by mutual consent ("Employment-At-Will"). This means that
employees have the right to terminate their employment at any time and for any
reason. Likewise, the Company reserves the right to discontinue your employment
with or without cause at any time and for any reason.

         The incentive plans as well as the employee benefit plans, programs and
practices as briefly outlined in this letter or attachments, reflect their
current provisions. Payments and benefits under these plans, programs, and
practices, as well as other payments referred to in this agreement, are subject
to IRS rules and regulations with respect to withholding, reporting, and
taxation, and will not be grossed-up unless specifically stated. Moreover, the
summaries contained herein are subject to the terms of such plans, programs and
practices.

         For purposes of the employee benefit plans, the definition of
compensation is as stated in the plans. All other compensation and payments
reflected in this offer are not included in the calculation of any employee
benefits.

         By acceptance of this agreement, you agree that (1) no trade secret or
proprietary information belonging to your employer prior to AT&T Corp. will be
intentionally disclosed or used by you at AT&T Wireless, and that no such
information, whether in the form of documents, memoranda, software or drawings,
etc., will be retained by you or brought with you to AT&T Wireless, and (2) you
have brought to AT&T Wireless's attention and provided it with a copy of any
agreement which may impact your future employment at AT&T Wireless, including
non-disclosure, non-competition, invention assignment agreements or agreements
containing future work restrictions. AT&T Wireless will not require or request
you to do anything that would intentionally violate clause (1) above.

         If you agree with the foregoing, and affirm that, to the best of your
knowledge, there are no agreements or other impediments that would prevent you
from providing exclusive service to the Company, please sign this agreement in
the space provided below and return the original executed copy to me.


                                              Sincerely,

                                              /s/ Harold W. Burlingame

                                              Harold W. Burlingame



/s/ Mohan Gyani                               June 20, 2001
----------------------------------------      ----------------------------------
Mohan Gyani                                   Date

Attachment


                                      -14-
<PAGE>   15
                                  ATTACHMENT A


Change in Control means:

(1)      an acquisition by any individual, entity or group (within the meaning
         of Section 13(d)(3) or 14(d)(2) of the Securities Exchange Act of 1934)
         (the "Exchange Act") (an "Entity") of beneficial ownership (within the
         meaning of Rule 13d-3 promulgated under the Exchange Act) of 20% or
         more of either (A) the then outstanding shares of stock of the Company
         (the "Outstanding Company Stock") or (B) the combined voting power of
         the then outstanding voting securities of the Company entitled to vote
         generally in the election of directors; excluding, however, certain
         acquisitions by or from the Company or by Company employee benefit
         plans or certain shareholder approved mergers or sale transactions
         involving the Company,

(2)      A change in the composition of our board of directors such that the
         individuals who, as of the effective date of the plan, constitute our
         board of directors, cease for any reason to constitute at least a
         majority of our board of directors, unless such change is approved by
         certain members of the current board,

(3)      With certain exceptions, the approval by the shareholders of the
         Company of a merger, reorganization or consolidation, or sale or other
         disposition of all or substantially all of the assets of AT&T Wireless
         or, if consummation of such corporate transaction is subject, at the
         time of such approval by shareholders, to the consent of any government
         or governmental agency, the obtaining of such consent, or

(4)      The approval by the shareholders of the Company of a complete
         liquidation or dissolution of the Company.


                                      -15-