<PAGE>

                                                                 Exhibit 10.13.2
                                                                 ---------------


                               IWO Holdings, Inc.
                      Independent Wireless One Corporation
                            319 Great Oaks Boulevard
                             Albany, New York 12203



                              September 1, 2000

Mr. David Standig
22 Gullane Drive
Slingerlands, New York 12159

     Re:  Stock Option Agreement, dated as of December 20, 1999 (the "First
          Stock Option Agreement"), between IWO Holdings, Inc. ("Holdings") and
          you; Stock Option Agreement, dated as of March 20, 2000 (the "Second
          Stock Option Agreement"), between Holdings and you; Warrant, dated
          December 20, 1999, to Purchase Shares of Class B Common Stock of IWO
          Holdings, Inc. granted to you (the "Warrant"); Employment Agreement,
          dated as of December 20, 1999 (the "Employment Agreement"), as
          amended, among Holdings, Independent Wireless One Corporation ("IWO")
          and you; Management Bonus Stock Purchase Agreement, dated as of
          December 20, 1999 (the "Bonus Stock Purchase Agreement"), among you,
          Holdings and IWO Holdings Limited; Management Stock Purchase
          Agreement, dated as of March 20, 2000 (the "Stock Purchase
          Agreement"), among you, Holdings and Investcorp IWO Limited
          Partnership.

Dear David:

     With reference to the above agreements, this letter agreement sets forth
certain understandings reached between Holdings, IWO and you.

     1.  Attached hereto as Exhibit A is a true and correct copy of the First
Stock Option Agreement.  Such First Stock Option Agreement shall be amended as
follows:

     (a) Section 1 shall be amended by deleting the definitions of "Approved
Sale," "Daily Vesting" and "Initial Public Offering" and replacing such
definitions with the following definitions:

         "Approved Sale" means a transaction or a series of related
          -------------
          transactions other than a Designated Merger:  (i) including, but not
          limited to, by way of merger or consolidation, which results in any
          "person" or "group" (as such terms are used in Sections 13(d) and
          14(d) of the Exchange Act or any successor provisions to either of the
          foregoing), other than (A) any one or more of the Initial Stockholders
          or Affiliates thereof or (B)  a non-U.S. entity with respect to which
          an Initial Stockholder or Affiliate thereof has an administrative
          relationship, becoming the "beneficial owner" (as defined in Rule 13d-
          3 under the Exchange Act), directly or indirectly, of a majority of
          the total voting power of the capital stock of Holdings or
<PAGE>

          otherwise able to elect a majority of the board of directors of
          Holdings (for purposes of this definition, such person or group shall
          be deemed to beneficially own capital stock of Holdings that is held
          by any other corporation so long as such person or group beneficially
          owns, directly or indirectly, in the aggregate a majority of the total
          capital stock of such other corporation); or (ii) which results in the
          sale, transfer, assignment, lease, conveyance or other disposition,
          directly or indirectly, of all or substantially all the assets of
          Holdings and its subsidiaries, considered as a whole (other than to an
          Affiliate thereof).

          "Daily Vesting" means vesting of the applicable portion of the Option
           --------------
          proportionately for each of the days during the applicable period that
          the Optionee is employed by Holdings such that if Optionee remains
          employed for all of the days during such applicable period such
          applicable portion of the Option shall be vested in full.

          "Initial Public Offering" means the sale of any of the common stock of
           -----------------------
          Holdings or the issuance of common stock of any Person in exchange for
          100% of the capital stock of Holdings pursuant to a registration
          statement that has been declared effective under the Act, if following
          such sale or exchange (i) the issuer is a reporting company under
          Section 12(b) or 12(g) of the Securities Exchange Act of 1934, as
          amended, and (ii) such stock is traded on the New York Stock Exchange
          or the American Stock Exchange, or is quoted on the Nasdaq National
          Market System or is traded or quoted on any other national stock
          exchange or national securities system.

     (b)  Section 1 shall be amended further by adding the following definition:

          "Designated Merger" means a transaction that results in the merger,
           -----------------
          consolidation or amalgamation of Holdings with or into any Person that
          results in the conversion of the outstanding shares of capital stock
          of Holdings into shares of capital stock of such Person (or its
          Affiliate) and such Person (or its Affiliate) has an affiliation with
          Sprint Spectrum L.P (or its Affiliates) similar to the affiliation
          between IWO and Sprint Spectrum L.P and its Affiliates (other than
          with respect to the territory covered).

     (c)  Section 3 shall be amended to add the following new clauses (c) and
          (d):

          "(c)  Upon the occurrence of an Initial Public Offering, the portion
          of the Performance Vesting Option that is not yet exercisable shall
          cease to vest on the basis of performance and, instead, shall vest on
          the basis of Daily Vesting over a period from January 1 of the year in
          which the closing of the Initial Public Offering occurs through
          December 31, 2002.

                                       2
<PAGE>

          (d)  Notwithstanding Section 3(a) and Section 3(b), upon the
          occurrence of a Designated Merger:

               (i) the schedule set forth in Section 3(a) shall not apply with
          respect to 20% of the Performance Vesting Options and Time Vesting
          Options that are not yet exercisable (and shall continue to apply to
          the remaining 80% of such options) and the Optionee shall have the
          right to exercise such 20% of all unexercisable Performance Vesting
          Options and Time Vesting Options; and

               (ii) if Optionee's employment is terminated by Holdings without
          Cause within 12 months following the closing of such Designated
          Merger, then the schedule set forth in Section 3(a) shall not apply
          with respect to the Performance Vesting Options and Time Vesting
          Options that are not yet exercisable and the Optionee shall have the
          right to exercise 100% of all unexercisable Performance Vesting
          Options and Time Vesting Options."

     (d)  Section 4 (b) shall be amended by deleting such section in its
entirety and replacing such section with the following:

          "(b)  The unexercisable portion of the Time Vesting Option and the
          Performance Vesting Option shall expire on the earlier to occur of (i)
          the Termination Date (giving effect to the vesting of such
          unexercisable portion in accordance with Section 3(d)(ii), if
          applicable), provided that, if prior to an Initial Public Offering, a
          pro rata portion of the portion of the Performance Vesting Option
          scheduled to become exercisable in the year including the Termination
          Date shall become exercisable as if the Optionee's employment had not
          been terminated if performance targets for the Fiscal Year during
          which the Termination Date have been met or exceeded, or (ii) except
          to the extent provided in Section 3(b), Section 3(d) and Section 6(a),
          an Approved Sale or a Designated Merger.  The proration provided for
          in clause (b)(i) above will be determined by the number of days
          elapsed in the year in which the termination occurred before the
          Termination Date.  The Performance Vesting Options that become
          exercisable pursuant to clause (b)(i) above shall expire one year
          following the date on which the Optionee received notice that the
          performance targets were met."

     (e)  Section 6(a) shall be amended by deleting such section in its entirety
and replacing such section with the following:

          "(a)  In the event of an Approved Sale or a Designated Merger, the
          unexercised portion of the Option shall terminate upon such Approved
          Sale or Designated Merger unless (i) provision is made in writing in
          connection with such Approved Sale or Designated Merger for the
          assumption of such Options, or for the substitutions of such Options
          of

                                       3
<PAGE>

          new awards covering the securities of a successor entity or an
          Affiliate thereof, with appropriate adjustments as to the number and
          kind of securities and exercise prices, in which event such
          outstanding Options shall continue or be replaced, as the case may be,
          in the manner and under the terms so provided; or (ii) the Board of
          Directors otherwise shall provide in writing for such adjustments as
          it deems appropriate in the terms and conditions of the then-
          outstanding Options, including without limitation (A) accelerating the
          vesting of outstanding Options and/or (B) providing for the
          cancellation of Options and their automatic conversion into the right
          to receive the securities, cash or other consideration that a holder
          of the shares underlying such Options would have been entitled to
          receive upon consummation of such Approved Sale or Designated Merger
          had such shares been issued and outstanding immediately prior to the
          closing date of the Approved Sale or Designated Merger (net of the
          appropriate option exercise prices). If pursuant to this Section 6(a)
          the Options are to terminate upon an Approved Sale or Designated
          Merger without provision for any of the actions described in clause
          (i) or (ii) above, then the Optionee shall be given at least ten (10)
          days' prior notice of the proposed Approved Sale or Designated Merger
          and shall be entitled to exercise such exercisable but unexercised
          portion of the Option (including all options that become exercisable
          immediately prior to the Approved Sale pursuant to Section 3(b) or the
          Designated Merger pursuant to Section 3(d)(i)) at any time during such
          ten (10) day period up to and until the close of business on the day
          immediately preceding the date of consummation of such Approved Sale
          or Designated Merger, and, notwithstanding Section 7 hereof, the
          Exercise Price may, at the option of the Optionee, be paid in whole or
          in part by delivery of shares of the Class B Common Stock owned by the
          Optionee (the value of such shares delivered as payment of the
          Exercise Price shall be determined based on and consistent with the
          value of the consideration to be tendered in connection with such
          Approved Sale or Designated Merger), and upon exercise of the Option
          the Option Shares shall be treated in the same manner as the shares of
          any other holder of Class B Common Stock."

     2.   Attached hereto as Exhibit B is a true and correct copy of the Second
Stock Option Agreement.  Such Second Stock Option Agreement shall be amended as
follows:

     (a) Section 1 shall be amended by deleting the definitions of "Approved
Sale" and "Initial Public Offering" and replacing such definitions with the
following definitions:

          "Approved Sale" means a transaction or a series of related
           -------------
          transactions other than a Designated Merger:  (i) including, but not
          limited to, by way of merger or consolidation, which results in any
          "person" or "group" (as such terms are used in Sections 13(d) and
          14(d) of the Exchange Act or any successor provisions to either of the
          foregoing), other than (A) any one or more of the Initial Stockholders
          or Affiliates thereof or (B)  a non-U.S. entity with respect to which
          an Initial Stockholder or Affiliate thereof

                                       4
<PAGE>

          has an administrative relationship, becoming the "beneficial owner"
          (as defined in Rule 13d- 3 under the Exchange Act), directly or
          indirectly, of a majority of the total voting power of the capital
          stock of Holdings or otherwise able to elect a majority of the board
          of directors of Holdings (for purposes of this definition, such person
          or group shall be deemed to beneficially own capital stock of Holdings
          that is held by any other corporation so long as such person or group
          beneficially owns, directly or indirectly, in the aggregate a majority
          of the total capital stock of such other corporation); or (ii) which
          results in the sale, transfer, assignment, lease, conveyance or other
          disposition, directly or indirectly, of all or substantially all the
          assets of Holdings and its subsidiaries, considered as a whole (other
          than to an Affiliate thereof).

          "Initial Public Offering" means the sale of any of the common stock of
           -----------------------
          Holdings or the issuance of common stock of any Person in exchange for
          100% of the capital stock of Holdings pursuant to a registration
          statement that has been declared effective under the Act, if following
          such sale or exchange (i) the issuer is a reporting company under
          Section 12(b) or 12(g) of the Securities Exchange Act of 1934, as
          amended, and (ii) such stock is traded on the New York Stock Exchange
          or the American Stock Exchange, or is quoted on the Nasdaq National
          Market System or is traded or quoted on any other national stock
          exchange or national securities system.

     (b)  Section 1 shall be amended further by adding the following definition:

          "Designated Merger" means a transaction that results in the merger,
           -----------------
          consolidation or amalgamation of Holdings with or into any Person that
          results in the conversion of the outstanding shares of capital stock
          of Holdings into shares of capital stock of such Person (or its
          Affiliate) and such Person (or its Affiliate) has an affiliation with
          Sprint Spectrum L.P (or its Affiliates) similar to the affiliation
          between IWO and Sprint Spectrum L.P and its Affiliates (other than
          with respect to the territory covered).

     (c)  Section 6(a) shall be amended by deleting such section in its entirety
and replacing such section with the following:

          "(a)  In the event of an Approved Sale or a Designated Merger, the
          unexercised portion of the Option shall terminate upon such Approved
          Sale or Designated Merger unless (i) provision is made in writing in
          connection with such Approved Sale or Designated Merger for the
          assumption of such Options, or for the substitutions of such Options
          of new awards covering the securities of a successor entity or an
          Affiliate thereof, with appropriate adjustments as to the number and
          kind of securities and exercise prices, in which event such
          outstanding Options shall continue or be replaced, as the case may be,
          in the manner and under

                                       5
<PAGE>

          the terms so provided; or (ii) the Board of Directors otherwise shall
          provide in writing for such adjustments as it deems appropriate in the
          terms and conditions of the then- outstanding Options, including
          providing for the cancellation of Options and their automatic
          conversion into the right to receive the securities, cash or other
          consideration that a holder of the shares underlying such Options
          would have been entitled to receive upon consummation of such Approved
          Sale or Designated Merger had such shares been issued and outstanding
          immediately prior to the closing date of the Approved Sale or
          Designated Merger (net of the appropriate option exercise prices). If
          pursuant to this Section 6(a) the Options are to terminate upon an
          Approved Sale or Designated Merger without provision for any of the
          actions described in clause (i) or (ii) above, then the Optionee shall
          be given at least ten (10) days' prior notice of the proposed Approved
          Sale or Designated Merger and shall be entitled to exercise such
          exercisable but unexercised portion of the Option at any time during
          such ten (10) day period up to and until the close of business on the
          day immediately preceding the date of consummation of such Approved
          Sale or Designated Merger, and, notwithstanding Section 7 hereof, the
          Exercise Price may, at the option of the Optionee, be paid in whole or
          in part by delivery of shares of the Class B Common Stock owned by the
          Optionee (the value of such shares delivered as payment of the
          Exercise Price shall be determined based on and consistent with the
          value of the consideration to be tendered in connection with such
          Approved Sale or Designated Merger), and upon exercise of the Option
          the Option Shares shall be treated in the same manner as the shares of
          any other holder of Class B Common Stock."

     3.  Attached hereto as Exhibit C is a true and correct copy of the
Employment Agreement.  You agree that in the case of a Designated Merger (as
defined in Section 1(b) hereof), the obligations of the parties under the
Employment Agreement with respect to Section 2 thereof will be satisfied if you
perform such duties and in such capacity or capacities as are commensurate with
your existing duties and capacities solely with respect to the current territory
covered by the business of IWO irrespective of the title you shall have after
such Designated Merger, or as otherwise agreed to between you and Holdings or
its successor in such Designated Merger.

     4.  Attached hereto as Exhibit D is a true and correct copy of the Warrant.
Such Warrant shall be amended as follows:

     (a) The words "or Panthers Merger" shall be inserted at the end of the
parenthetical clause in the heading thereof (appearing below the legend);

     (b) The words "or upon a Panthers Merger" shall be added to the end of the
first sentence in the first full paragraph following the heading thereof;

     (c) Section 1 shall be amended by deleting the definition of "Approved
Sale" and replacing such definition with the following definition:

                                       6
<PAGE>

          "Approved Sale" means a transaction or a series of related
            -------------
          transactions other than a Panthers Merger:  (i) including, but not
          limited to, by way of merger or consolidation, which results in any
          "person" or "group" (as such terms are used in Sections 13(d) and
          14(d) of the Exchange Act or any successor provisions to either of the
          foregoing), other than (A) any one or more of the Initial Stockholders
          or Affiliates thereof or (B)  a non-U.S. entity with respect to which
          an Initial Stockholder or Affiliate thereof has an administrative
          relationship, becoming the "beneficial owner" (as defined in Rule 13d-
          3 under the Exchange Act), directly or indirectly, of a majority of
          the total voting power of the capital stock of Holdings or otherwise
          able to elect a majority of the board of directors of Holdings (for
          purposes of this definition, such person or group shall be deemed to
          beneficially own capital stock of Holdings that is held by any other
          corporation so long as such person or group beneficially owns,
          directly or indirectly, in the aggregate a majority of the total
          capital stock of such other corporation); or (ii) which results in the
          sale, transfer, assignment, lease, conveyance or other disposition,
          directly or indirectly, of all or substantially all the assets of
          Holdings and its subsidiaries, considered as a whole (other than to an
          Affiliate thereof).

     (d)  Section 1 shall be amended further by adding the following definition:

          "Panthers Merger" means a transaction that (i) results in the merger,
           ---------------
          consolidation or amalgamation or other business combination of
          Holdings with or into an entity referred to by Holdings as "Panthers,"
          or the sale, transfer, assignment, lease, conveyance or other
          disposition, directly or indirectly, of all or substantially all the
          assets of Holdings and its subsidiaries, considered as a whole, to
          Panthers, and (ii) closes prior to March 31, 2001.

     (e)  Section 2(a)(ii) shall be amended to delete the "or" at the end of
Section 2(a)(ii).

     (f) Section 2(a)(iii) shall be amended to replace the "." at the end of
Section 2(a)(iii) with "; or".

     (g) Section 2(a) shall be amended to add the following new clause (iv):

          "(iv)  immediately prior to the closing of a Panthers Merger."

     (h) Section 2(b)(ii) shall be amended to delete the "or" at the end of
Section 2(b)(ii).

     (i) Section 2(b)(iii) shall be amended to replace the "." at the end of
Section 2(b)(iii) with "; or".

     (j) Section 2(b) shall be amended to add the following new clause (iv):

          "(iv)  immediately prior to the closing of a Panthers Merger."

                                       7
<PAGE>

     (k)  Section 2(c) shall be amended by deleting such section in its entirety
and replacing such section with the following:

          "(c)  Holdings shall give to the Holder written notice (the "Holdings
                                                                       --------
          Notice") of the occurrence of an Approved Sale or a Panthers Merger at
          ------
          least 20 days prior to the anticipated closing of such Approved Sale
          or Panthers Merger or an Initial Investors Cash-Out within 100 days
          following such Initial Investors Cash-Out."

     (l)  Section 2(f) shall be amended by deleting such section in its entirety
and replacing such section with the following:

          "(f)  (i) If the Holdings Notice is with respect to a Panthers Merger,
          the Holder shall notify Holdings on or before five days prior to the
          anticipated closing date of such Panthers Merger of such Holder's
          exercise; (ii) with respect to an Approved Sale, if the Holdings
          Notice states that Holdings anticipates that such event will cause the
          vesting of the 40% IRR Warrant or the 60% IRR Warrant, the Holder
          shall notify Holdings on or before five days prior to the anticipated
          closing date of such Approved Sale of such Holder's exercise; and
          (iii) with respect to an Initial Investors Cash-Out, if the Holdings
          Notice states that such event has caused the vesting of either of such
          warrants, the Holder shall notify Holdings on or before five days
          following receipt of the Holdings Notice of such Holder's exercise of
          this Warrant (the "Notice Date") .  This Warrant shall be exercisable
                             -----------
          by the Holder in whole only, and not in part, by the surrender of this
          Warrant and delivery to Holdings on or before the Notice Date of (i) a
          duly executed notice of exercise in the form of Exhibit A (a "Notice
                                                                        ------
          of Exercise") and (ii) at the option of the Holder, either (A) the
          -----------
          Exercise Price for the Warrant Shares, payable in cash or by wire
          transfer to a bank account designated by Holdings or (B) in the case
          of a Panthers Merger, a notice by Holder to Holdings requesting the
          Warrant Shares be issued net of the appropriate Exercise Price (to be
          determined based on and consistent with the value of the consideration
          to be tendered in connection with such Panthers Merger)."

     (m) Section 2(g) shall be amended by deleting such section in its entirety
and replacing such section with the following:

          "(g)  This Warrant shall terminate automatically upon the closing of
          an Approved Sale or a Panthers Merger and this Warrant shall no longer
          be of any force or effect, unless (i) provision is made in writing in
          connection with such transaction for the continuance of this Warrant
          and for the assumption of this Warrant, or for the substitution for
          this Warrant of a new Warrant covering the securities of a successor
          entity or an affiliate thereof, with appropriate adjustments as to the
          number and kind of securities and exercise price, in which event this
          Warrant shall continue or be replaced, as the case may be, in the
          manner and under the terms so

                                       8
<PAGE>

          provided; or (ii) the Board of Directors of Holdings shall provide in
          writing for such adjustment as it deems appropriate in terms and
          conditions of this Warrant, including without limitation (A)
          accelerating the vesting of this Warrant and/or (B) providing for the
          cancellation of this Warrant and its automatic conversion into the
          right to receive the securities, cash or other consideration that the
          Holder would have been entitled to receive upon consummation of such
          Approved Sale or Panthers Merger had Warrant Shares been issued and
          outstanding immediately prior to the Approved Sale or Panthers Merger
          (net of the appropriate exercise price)."

     5.  Attached hereto as Exhibit E is a true and correct copy of the Bonus
Stock Purchase Agreement.  Attached hereto as Exhibit F is a true and correct
copy of the Stock Purchase Agreement.  Upon the occurrence of a Panthers Merger
(as defined in Section 4(d) hereof):

     (a) with respect to the Bonus Stock Purchase Agreement, Holdings hereby
waives any Repurchase Right (as defined therein) that it may have pursuant to
Section 3(a) thereof and you hereby waive any Put Right (as defined therein)
that you may have pursuant to Section 3(b) thereof; and

     (b) with respect to the Stock Purchase Agreement, Holdings hereby waives
any Repurchase Right (as defined therein) that it may have pursuant to Section
3(a) thereof and you hereby waive any Put Right (as defined therein) that you
may have pursuant to Section 3(b) thereof.

     6.  Except for the changes described herein, the First Stock Option
Agreement, the Second Stock Option Agreement, the Warrant, the Employment
Agreement, the Bonus Stock Purchase Agreement and the Stock Purchase Agreement
will be unchanged and remain in full force and effect.

     7.  In connection with a Designated Merger if and when requested by the
board of directors of Holdings, you agree to enter into a lockup agreement and a
voting agreement with respect to your shares of capital stock of Holdings and
Parent and any such capital stock that may be acquired upon the exercise of
options or warrants for such capital stock, to the extent and on substantially
the same basis as Investcorp S.A. and its subsidiaries enter into such
agreements with respect to their capital stock of Holdings and Parent.

     8.  You hereby waive any acceleration of benefits pursuant to the First
Stock Option Agreement, the Second Stock Option Agreement, the Warrant, the
Bonus Stock Purchase Agreement or the Stock Purchase Agreement unless
shareholder approval meeting the requirements of Section 280G(b)(5) of the
Internal Revenue Code of 1986, as amended (the "Code"), with respect to such
benefits is obtained.

     9.  You agree that this letter agreement (excluding for this purpose
paragraph 8 of such agreement) shall not be effective unless shareholder
approval meeting the requirements of Section 280G(b)(5) of the Code is obtained.

                                       9
<PAGE>

     10.  This letter agreement shall inure to the benefit of, and be binding
upon, the heirs, executors, administrators, successors and assigns of you,
Holdings and/or IWO.

     11.  The parties hereto agree to take or cause to be taken all such further
actions as may be reasonably necessary or appropriate to effectuate the intent,
purposes and obligations of this letter agreement.





                                      10
<PAGE>

     Please indicate your acceptance of the terms hereof by signing in the
appropriate space below.

                              Very truly yours,


                              IWO HOLDINGS, INC.



                              By: /s/ Solon L. Kandel
                                 --------------------
                                 Name:  Solon L. Kandel
                                 Title:  President and Chief Executive Officer



                              INDEPENDENT WIRELESS ONE CORPORATION



                              By: /s/ Solon L. Kandel
                                 --------------------
                                 Name:  Solon L. Kandel
                                 Title:  President and Chief Executive Officer

Agreed and accepted:

David Standig


/s/ David L. Standig
--------------------