<PAGE>   1
                                                                   EXHIBIT 10.38




                               RETENTION AGREEMENT

                  This Agreement (this "Agreement") is made as of the 22nd day
of December, 2000, between Deutsche Telekom AG, an AKTIENGESELLSCHAFT organized
and existing under the laws of the Federal Republic of Germany ("Deutsche
Telekom"), and VoiceStream Wireless Corporation, a Delaware corporation
("VoiceStream").

                                WITNESSETH THAT:

                  WHEREAS, Deutsche Telekom and VoiceStream are parties to an
Agreement and Plan of Merger dated as of July 23, 2000 as amended and restated
on September 28, 2000 (the "Merger Agreement");

                  WHEREAS, in connection with the negotiation and execution of
the Merger Agreement, the parties engaged in significant discussions regarding
the establishment and implementation of retention arrangements and, in
particular, the establishment of an equity incentive plan, to motivate senior
management employees of VoiceStream and its subsidiaries (including key
personnel and key managers as such terms are used in the VoiceStream Option Plan
(as defined herein)) to continue employment with VoiceStream and its
subsidiaries or their respective successors following the consummation of the
transactions contemplated by the Merger Agreement;

                  WHEREAS, in recognition of the importance to the parties of
the establishment and implementation of retention arrangements, the parties
agreed pursuant to Section 5.19(d) of the Merger Agreement that, during the
sixty-day period following the date of execution of the original Merger
Agreement (the "Merger Agreement Date"), they would seek to develop a mutually
acceptable retention plan for senior management employees of VoiceStream and its
subsidiaries (including key personnel and key managers as such terms are used in
the VoiceStream Option Plan) with the intention that such retention arrangement
would include an equity incentive component in respect of DT Ordinary Shares;

                  WHEREAS, the parties have agreed to extend such sixty-day
period to December 22, 2000;

                  WHEREAS, VoiceStream currently maintains the VoiceStream
Management Incentive Stock Option Plan (the "VoiceStream Option Plan") to
provide an incentive to senior management employees of VoiceStream and its
subsidiaries (including key personnel and key managers as such terms are used in
the VoiceStream Option Plan) to remain in the employ of VoiceStream or its
subsidiaries;

                  WHEREAS, pursuant to Section 5.19(d) of the Merger Agreement,
the parties have agreed that following the Closing, Deutsche Telekom shall, as
agreed upon with VoiceStream prior to the Closing, make such amendments as are
necessary to modify the VoiceStream Option Plan to permit the issuance of
options to purchase DT Ordinary Shares (the "Retention Options") following the
Closing to senior management employees of VoiceStream and its subsidiaries
(including key personnel and key managers as such terms are used in the


                                       1
<PAGE>   2
VoiceStream Option Plan) pursuant to the general terms and conditions of the
VoiceStream Option Plan, as amended from time to time by Deutsche Telekom;

                  WHEREAS, to effectuate the foregoing, the parties have agreed
that effective as of the Closing Date, Deutsche Telekom will establish a Trust
(as described in Section 2 of this Agreement) to issue Retention Options during
the period beginning on the Closing Date and continuing through December 31,
2004;

                  WHEREAS, as partial consideration for the contribution by the
Surviving Corporation of the Surviving Corporation Common Stock to the Escrow
Agent and the delivery by the Escrow Agent of such Surviving Corporation Common
Stock to Deutsche Telekom, VoiceStream and Deutsche Telekom have agreed in
accordance with the Merger Agreement that 8,000,000 DT Ordinary Shares be issued
and placed in a Trust (as described in Section 2 of this Agreement) for the
purpose of satisfying the obligations created by the issuance of the Retention
Options.

                  NOW, THEREFORE, further to Section 5.19(d) of the Merger
Agreement and in order to provide an incentive to the key management employees
of VoiceStream and its subsidiaries (including key personnel and key managers as
such terms are used in the VoiceStream Option Plan) for the continued dedication
of such employees, and for other good and valuable consideration, Deutsche
Telekom and VoiceStream hereby agree as follows:

                  1. Certain Definitions. All capitalized terms used and not
defined herein shall have the meaning assigned to such terms in the Merger
Agreement.

                  2. Establishment of Trust. On the Closing Date, as soon as
possible after the Effective Time, in order to fulfill the obligations set forth
herein, Deutsche Telekom shall issue 8,000,000 DT Ordinary Shares as partial
consideration for the contribution by the Surviving Corporation of the Surviving
Corporation Common Stock to the Escrow Agent and the delivery by the Escrow
Agent of such Surviving Corporation Common Stock to Deutsche Telekom. Such DT
Ordinary Shares shall be transferred to and held in a U.S. trust pursuant to a
form of trust agreement to be mutually agreed upon, the terms and conditions of
which shall be consistent with the terms and conditions of the Option Trust
described in Annex 1.08(a) of the Merger Agreement (the "Trust") and used solely
to satisfy the obligations pursuant to the exercise of the Retention Options. In
the event of any corporate transaction involving the DT Ordinary Shares,
including without limitation a stock split, stock dividend, spin-off, merger or
reorganization, the number and kind of shares in the Trust shall be
appropriately and equitably adjusted. These 8,000,000 DT Ordinary Shares are in
addition to the DT Ordinary Shares that will be delivered to the Options Trust
pursuant to Section 1.08 of the Merger Agreement. The options described in
Sections 4 and 5 of this Agreement shall be encompassed by the provisions of
Section 1.08 of the Merger Agreement.

                  3. Continuation of VoiceStream Plan. In connection with the
Closing, Deutsche Telekom shall, as agreed upon with VoiceStream prior to the
Closing, make such amendments as are necessary to modify the VoiceStream Option
Plan to permit the issuance of the Retention

                                       2
<PAGE>   3
Options. For the period beginning on the Closing Date and continuing through
December 31, 2004, Deutsche Telekom shall cause the Trust to issue Retention
Options to senior management employees of VoiceStream and its subsidiaries
(including key personnel and key managers as such terms are used in the
VoiceStream Option Plan) substantially on the terms set forth in the VoiceStream
Option Plan, as amended from time to time by Deutsche Telekom.

                  4. Additional Option Grants. Pursuant to Section 5.19(d) of
the Merger Agreement, Deutsche Telekom and VoiceStream have agreed that
VoiceStream may grant at any time after the Merger Agreement Date to 31 managers
a number of VoiceStream options (the "Additional Options") equal to the unvested
VoiceStream options held by such managers as of the Merger Agreement Date that
provide by their terms for accelerated vesting upon a change of control of
VoiceStream (other than the portion of those options that would vest in the
ordinary course following the Merger Agreement Date and prior to May 31, 2001)
(the "Unvested Options"). The Additional Options shall have the same terms and
conditions, including exercise price and continuing vesting schedule, as the
outstanding Unvested Options with respect to which they are granted, except that
such Additional Options will not vest on a change of control of VoiceStream or
any of its successors. A maximum of 574,368 Additional Options may be granted
under this provision, and such Additional Options shall not reduce the amount of
options VoiceStream is otherwise permitted to grant, pursuant to Section 4.01(a)
of the Merger Agreement, prior to the Closing. In exchange for the grant of
Additional Options, the optionee will be required to waive change of control
vesting of the optionee's existing options in connection with any change of
control of VoiceStream or any of its successors, but such options will continue
to vest pursuant to their terms. In the event that an optionee's employment is
terminated by the optionee's employer without cause or due to a reduction in
force, due to the optionee's death or disability or by the optionee as a result
of a constructive termination (reduction in pay), all of the remaining Unvested
Options shall become vested and exercisable (and any unvested Additional Options
will vest only if otherwise provided in the applicable award agreement or any
other applicable agreement between VoiceStream and the optionee).
Notwithstanding the foregoing, if the optionee's employment terminates for any
reason other than as set forth in the preceding sentence, except as provided in
any applicable agreement between VoiceStream and the optionee, all Unvested
Options (and any unvested Additional Options) shall be terminated.

                  5. Other Options. DT acknowledges that pursuant to Section
4.01(a) of the Merger Agreement, VoiceStream will be permitted to grant to its
directors, officers and employees up to 1,500,000 options in addition to the
Additional Options prior to Closing.

                  6. Retention Program. DT acknowledges that VoiceStream shall
be permitted to provide a retention program to its employees in an amount up to
$100 million pursuant to the terms of Schedule 4.01(e) of the Merger Agreement.

                  7. Modification; Waiver. No provisions of this Agreement may
be modified, waived or discharged unless such waiver, modification or discharge
is agreed to in a writing signed by each of the parties hereto. Waiver by any
party of any breach of or failure to comply with any provision of this Agreement
by the other party shall not be construed as, or constitute, a

                                       3
<PAGE>   4
continuing waiver of such provision, or a waiver of any other breach of, or
failure to comply with, any other provision of this Agreement.

                  8. Notice. All notices and other communications given or made
pursuant hereto shall be in writing and shall be deemed to have been duly given
or made as of the date of receipt and shall be delivered personally or mailed by
registered or certified mail (postage prepaid, return receipt requested), sent
by overnight courier or sent by telecopy, to the parties at the following
addresses or telecopy numbers (or at such other address or telecopy number for a
party as shall be specified by like notice):

                  if to VoiceStream:
                  VoiceStream Wireless Corporation
                  12920 SE 38th Street
                  Bellevue, Washington  98006
                  Attention:  Alan R. Bender
                  Facsimile:  425-586-8080

                  with a copy to:

                  Wachtell, Lipton, Rosen & Katz
                  51 West 52nd Street
                  New York, New York  10019
                  Attention: Michael Katzke
                  Facsimile: 212-403-2000

                  if to Deutsche Telekom:
                  Deutsche Telekom AG
                  140 Friedrich-Ebert Allee
                  53113 Bonn
                  Germany
                  Attention:  Kevin Copp
                  Facsimile:  49-228-181-44177

                  with a copy to:

                  Cleary, Gottlieb, Steen & Hamilton
                  One Liberty Plaza
                  New York, New York  10006
                  Attention:  A. Richard Susko
                  Facsimile:  212- 225-3999

                  and a copy to

                  Hengeler Mueller
                  Trinkausstrasse 7


                                       4
<PAGE>   5
                  D-40213 Dusseldorf
                  Germany
                  Attention:  Rainer Krause or Maximilian Schiessl

                  9. Severability. If any term or provision of this Agreement or
the application thereof to any person or circumstance shall to any extent be
invalid or unenforceable, the remainder of this Agreement or the application of
such term or provision to persons or circumstances other than those as to which
it is held invalid or unenforceable shall not be affected thereby, and each term
and provision of this Agreement shall be valid and enforceable to the fullest
extent permitted by law.

                  10. Headings. The headings in this Agreement are inserted for
convenience of reference only and shall not be a part of or control or affect
the meaning of this Agreement.

                  11. Counterparts. This Agreement may be executed in several
counterparts, each of which shall be deemed an original.

                  12. Governing Law. This Agreement has been executed and
delivered in the State of New York and shall in all respects be governed by, and
construed and enforced in accordance with, the laws of the State of New York,
without reference to its principles of conflicts of law.




                                       5
<PAGE>   6
                  IN WITNESS WHEREOF, the parties have executed this Agreement
as of the date first written above.



                                        DEUTSCHE TELEKOM AG

                                        /s/     Jeffrey Hedberg
                                        ------------------------------
                                        By:     Jeffrey Hedberg
                                        Title:  Member of the Board of
                                                Management, International


                                        VOICESTREAM WIRELESS CORPORATION

                                        /s/     John Stanton
                                        ------------------------------
                                        By:     John Stanton
                                        Title:  Chairman of the Board and
                                                Chief Executive Officer
                                                (Principal Executive Officer)





                                       6