<PAGE>   1

                                                                     EXHIBIT 4.3

                                                  POWERTEL STOCKHOLDER AGREEMENT

                         POWERTEL STOCKHOLDER AGREEMENT

     This Stockholder Agreement (this "AGREEMENT") dated as of August 26, 2000
between the stockholders listed on the signature page hereto (collectively,
the "STOCKHOLDER") and Deutsche Telekom AG, an Aktiengesellschaft organized
and existing under the laws of the Federal Republic of Germany ("DT").

     WHEREAS, simultaneously with the execution of this Agreement, Powertel,
Inc., a Delaware corporation (the "POWERTEL"), and DT are entering into an
Agreement and Plan of Merger dated as of the date hereof providing for the
merger of a subsidiary of DT with and into Powertel (as amended or modified from
time to time, the "DT MERGER AGREEMENT");

     WHEREAS, DT has agreed to enter into the DT Merger Agreement only if the
Stockholder enters into this Agreement;

     WHEREAS, simultaneously with the execution of this Agreement, Powertel and
VoiceStream Wireless Corporation, a Delaware corporation ("VOICESTREAM"), are
entering into an Agreement and Plan of Reorganization (as amended or modified
from time to time, the "VOICESTREAM REORGANIZATION AGREEMENT"), dated as of the
date hereof, providing for, among other things, the merger of a subsidiary of
VoiceStream with and into Powertel if, but only if, the DT Merger Agreement is
terminated;

     NOW THEREFORE, in consideration of the foregoing and the mutual premises,
representations, warranties, covenants and agreements contained herein and in
the DT Merger Agreement, the parties hereto, intending to be legally bound
hereby, agree as follows:

     1.   CERTAIN DEFINITIONS.  This Agreement is one of the Powertel
Stockholder Agreements referred to in the recitals to the DT Merger Agreement.
Capitalized terms used but not defined in this Agreement are used in this
Agreement with the meanings given to such terms in the DT Merger Agreement. In
addition, for purposes of this Agreement the following terms shall have the
following meanings:

     "BENEFICIALLY OWNED" or "BENEFICIAL OWNERSHIP" shall include, with respect
to any securities, the beneficial ownership of such securities by a Stockholder
and by any direct or indirect Subsidiary of a Stockholder.

     "DT DERIVATIVE SECURITIES" means any security convertible into or
exchangeable for DT Securities or the value of which is derived from the value
of DT Securities.

     "DT SECURITIES" means DT Ordinary Shares and DT Depositary Shares, each
representing the right to receive one DT Ordinary Share, and any security into
which DT Ordinary Shares or DT Depositary Shares are exchangeable as
contemplated by Section 1.05(f) of the DT Merger Agreement.

     "TRANSFER" means, with respect to any security, the sale, transfer,
pledge, hypothecation, encumbrance, assignment or constructive sale or other
disposition  of such security or the Beneficial Ownership thereof, the offer to
make such a sale, transfer, constructive sale or other


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disposition, and each option, agreement, arrangement or understanding, whether
or not in writing, to effect any of the foregoing. The term "CONSTRUCTIVE SALE"
means a short sale with respect to such security, entering into or acquiring an
offsetting derivative contract with respect to such security, entering into or
acquiring a futures or forward contract to deliver such security or entering
into any transaction that has substantially the same effect as any of the
foregoing; PROVIDED, HOWEVER, that the term "constructive sale" shall not
include transactions involving the purchase and sale of securities tracking a
broad-based stock index excluding the DAX Index.

     "VOICESTREAM/DT MERGER AGREEMENT" means the Agreement and Plan of Merger
between Parent and DT dated as of July 23, 2000, as it may be amended or
modified from time to time.

     2.   REPRESENTATIONS; WARRANTIES AND COVENANTS OF STOCKHOLDER. Stockholder
hereby represents and warrants, severally and not jointly, to DT, solely with
respect to itself, as of the date hereof, as follows:

     2.1  TITLE. As of the date hereof, Stockholder is the sole record and
Beneficial Owner of the number of shares of Powertel Common Stock or Powertel
Preferred Stock, as the case may be, set forth opposite Stockholder's name on
Schedule A attached hereto (Stockholder's "Existing Shares" and, together with
the record ownership or Beneficial Ownership of any shares of Powertel Common
Stock, Powertel Preferred Stock or other voting capital stock of Powertel
acquired after the date hereof, whether upon the exercise of warrants or
options, conversion of the Powertel Preferred Stock or any convertible
securities or otherwise, Stockholder's "Shares"), and/or the number of warrants,
options or other rights to acquire or receive such Powertel Common Stock or
Powertel Preferred Stock, as the case may be, set forth opposite Stockholder's
name on Schedule A attached hereto (Stockholder's "Existing Rights" and,
together with record ownership or Beneficial Ownership of any warrants, options
or other rights to acquire or receive such shares of Powertel Common Stock,
Powertel Preferred Stock or other voting capital stock of Powertel acquired
after the date hereof, Stockholder's "Rights"). Stockholder is the lawful owner
of the Existing Shares and Existing Rights, free and clear of all liens, claims,
charges, security interests or other encumbrances, except as disclosed on
Schedule A. As of the date hereof, the Existing Shares constitute all of the
capital stock of Powertel Beneficially Owned or owned of record by Stockholder
(excluding the Existing Rights) and Stockholder does not own of record or
beneficially, or have the right to acquire (whether currently, upon lapse of
time, following the satisfaction of any conditions, upon the occurrence of any
event or any combination of the foregoing) any shares of Powertel Common Stock
or Powertel Preferred Stock or any other securities convertible into or
exchangeable or exercisable for shares of Powertel Common Stock or Powertel
Preferred Stock, except pursuant to the Existing Rights.

     2.2  RIGHT TO VOTE. Stockholder has, with respect to all of Stockholder's
Existing Shares, and will have at the Powertel Stockholders' Meeting, with
respect to all of Stockholder's Shares acquired prior to the record date for the
Powertel Stockholders' Meeting, sole voting power, sole power of disposition or
sole power to issue instructions with respect to the matters set forth in
SECTION 4 hereof and to fulfill its obligations under such Section and shall not
take any action or grant any person any proxy (revocable or irrevocable) or
power-of-attorney with respect to any Shares or Rights inconsistent with his or
its obligations as provided


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by SECTION 4 AND SECTION 5 hereof. Stockholder hereby revokes any and all
proxies with respect to Stockholder's Existing Shares or Existing Rights to the
extent they are inconsistent with the Stockholders' obligations under this
Agreement.

     2.3  AUTHORITY.  Stockholder has full legal power, authority, legal
capacity and right to execute and deliver, and to perform its or his obligations
under, this Agreement. No other proceedings or actions on the part of
Stockholder are necessary to authorize the execution, delivery or performance of
this Agreement or the consummation of the transactions contemplated hereby. This
Agreement has been duly and validly executed and delivered by Stockholder and
constitutes a valid and binding agreement of Stockholder enforceable against
Stockholder in accordance with its terms, subject to (i) bankruptcy, insolvency,
moratorium and other similar laws now or hereafter in effect relating to or
affecting creditors rights generally and (ii) general principles of equity
(regardless of whether considered in a proceeding at law or in equity).

     2.4  CONFLICTING INSTRUMENTS.  Neither the execution and delivery of this
Agreement, nor the performance by Stockholder of its agreements and obligations
hereunder will result in any breach or violation of, or be in conflict with or
constitute a default under, any term of any agreement, judgment, injunction,
order, decree, law or regulation to which Stockholder is a party or by which
Stockholder (or any of its assets) is bound.

     2.5  DT'S RELIANCE.  Stockholder understands and acknowledges that DT is
entering into the DT Merger Agreement in reliance upon Stockholder's execution,
delivery and performance of this Agreement.

     3.   RESTRICTION ON TRANSFER; OTHER RESTRICTIONS.

     3.1  Stockholder agrees not to Transfer or agree to Transfer any Shares or
Rights owned of record or Beneficially Owned by Stockholder, except as otherwise
permitted by this Section 3 or pursuant to the DT Merger Agreement, Transfers to
any Affiliate of the Stockholder who agrees in writing to be bound by the terms
of this Agreement or Transfers which occur by operation of law if the transferee
remains, or agrees in writing to remain, bound by the terms of this Agreement,
other than, in each case, with DT's prior written consent.

     3.2  From the date hereof until the later of January 1, 2001 and the date
of the Powertel Stockholders' Meeting, Stockholder agrees not to Transfer any
Shares or Rights owned of record or Beneficially Owned by Stockholder, provided,
however, that this SECTION 3.2 shall cease to be of any force or effect
immediately upon termination of the DT Merger Agreement.

     3.3  From the later of January 1, 2001 and the date of the Powertel
Stockholders' Meeting until the earlier of the Effective Time or the termination
of the DT Merger Agreement, Stockholder may Transfer only up to 17.5% of
Stockholder's Total Number of Shares; provided, however, that if the Effective
Time shall not have occurred by July 31, 2001, the percentage specified in this
SECTION 3.3 shall on August 1, 2001 be increased by 3.75% and, if the Effective
Time shall not have occurred by August 31, 2001, the percentage specified in
this SECTION 3.3 shall on September 1, 2001 be increased by an additional 3.75%,
for an aggregate amount from and after September 1, 2001 of 25%.

     3.4  From the Effective Time through and including the three month
anniversary of the Effective Time, Stockholder agrees not to Transfer any DT
Securities or DT Derivative Securities.

     3.5  From the day following the three month anniversary of


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the Effective Time, through and including the six month anniversary of the
Effective Time, Stockholder may Transfer only up to 40% of Stockholder's Total
Number of Shares, inclusive of any Transfer of any DT Derivative Securities.

     3.6  For the avoidance of doubt, the portions of a Stockholder's Total
Number of Shares permitted to be Transferred pursuant to SECTION 3.3 AND SECTION
3.5 are (i) separate and not cumulative such that if a Stockholder does not
fully utilize the permission to Transfer up to 17.5% of Stockholder's Total
Number of Shares pursuant to SECTION 3.3, Stockholder shall not be permitted to
Transfer more than 40% of Stockholder's Total Number of Shares pursuant to
SECTION 3.5 and (ii) exclusive of any Transfers permitted by this Agreement
which occur at any time after the date hereof and prior to the end of the
periods specified in such Sections.

     3.7  For purposes of SECTION 3.3, a Stockholder's "Total Number of Shares"
is equal to the sum (such sum, the "INITIAL NUMBER OF SHARES") of (i) the number
of shares of Powertel Stock owned of record or Beneficially Owned by the
Stockholder as of the later of January 1, 2001 and the date of the Powertel
Stockholders' Meeting, including any shares of Powertel Common Stock issuable
upon conversion of any shares of Powertel Preferred Stock owned by the
Stockholder and (ii) the number of shares of Powertel Common Stock owned of
record or Beneficially Owned by the Stockholder as a result of the exercise or
conversion, as applicable, of any options, warrants or convertible securities
(other than Powertel Preferred Stock) to acquire shares of Powertel Common
Stock, during the period from the later of January 1, 2001 and the date of the
Powertel Stockholders' Meeting, until the earlier of the Effective Time and the
termination of the DT Merger Agreement. For purposes of SECTION 3.5,
Stockholder's Total Number of Shares is equal to the sum of (A) the number of DT
Securities which the Stockholder has received or may be entitled to receive as
the Merger Consideration pursuant to the DT Merger Agreement in respect of the
Initial Number of Shares and (B) the number of DT Securities owned of record or
Beneficially Owned by the Stockholder as a result of the exercise or conversion,
as applicable, of any options, warrants or convertible securities to acquire DT
Securities (other than any such options, warrants or convertible securities
included in the calculation of the Initial Number of Shares), during the
forth relevant period specified in SECTION 3.5.

     3.8  The foregoing limitations set forth in SECTIONS 3.3 AND 3.5 shall
not apply to any Transfers pursuant to a tender offer, self tender offer,
exchange offer or other transaction offered generally to holders of DT
Securities approved or not opposed by DT's Supervisory Board, and securities
subject to a Transfer made pursuant to this SECTION 3.8 shall be deemed
continued to be owned by the Stockholder for purposes of the calculations made
under SECTION 3.3 and 3.5.

     3.9  Stockholder agrees, prior to the Effective Time, not to effect,
directly or indirectly, or through any arrangement with a third party pursuant
to which such third party may effect, directly or indirectly, any short sales of
any Powertel Stock, DT Securities or DT Derivative Securities except in
accordance with the limitations of Section 3.3.

     3.10 Stockholder hereby irrevocably waives any rights of appraisal or
rights to dissent from the merger contemplated by the DT Merger Agreement that
Stockholder may have.

     3.11 If DT acquires any company after the date hereof for consideration
valued at more than $15 billion and, at the time the agreement in respect of
such acquisition by DT is entered into, (i) such company has a single
stockholder who owns 10% or more or a group of stockholders owning in


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the aggregate 20% or more of the outstanding voting securities of such company
and (ii) in each case such stockholders are (or at any time within the prior
two years were) directors of or have the right to designate one or more
directors to the Board of Directors of such company or are officers of such
company or such company has any 5% or greater stockholders (other than
institutional investors) as to whom DT could reasonably enter into an agreement
in support of such acquisition and DT obtains or could reasonably be expected
to obtain the agreement of any such stockholder or group of stockholders of
such company, as the case may be, to vote for and support the acquisition or to
limit its powers of disposition in connection with the acquisition, the
transfer restrictions specified in SECTION 3.1 THROUGH 3.5 shall be revised to
reflect the more favorable treatment of the stockholders of such company or the
absence of restrictions, as the case may be, including the grant or sufferance
to exist of registration rights.

     4.   AGREEMENT TO VOTE.  Stockholder hereby irrevocably and
unconditionally agrees to vote or to cause to be voted, or provide a consent
with respect to, all Shares that it owns of record or beneficially as of the
record date for the Powertel Stockholders' Meeting at the Powertel
Stockholders' Meeting and at any other annual or special meeting of
stockholders of Powertel or action by written consent where such matters arise
(a) in favor of the Merger and the DT Merger Agreement and approval of the
terms thereof and each of the other transactions contemplated thereby and
(b) against, and will not consent to, (i) approval of any Alternative
Transaction or (ii) the liquidation or winding up of Powertel. The obligations
of each Stockholder specified in this SECTION 4 shall apply whether or not the
Board of Directors of Powertel makes a Subsequent Determination.

     5.   DELIVERY OF PROXY.  In furtherance of the agreements contained in
Section 4 hereof, Stockholder hereby agrees (a) to complete and send the proxy
card received by Stockholder with the Powertel Proxy Statement, so that such
proxy card is received by Powertel, as prescribed by the Powertel Proxy
Statement, not later than the fifth Business Day preceding the day of the
Powertel Stockholders' Meeting, (b) to vote, by completing such proxy card but
not otherwise, all the Shares it owns of record or Beneficially Owns as of the
record date for the Powertel Stockholders' Meeting (i) in favor of the Merger
and the DT Merger Agreement and (ii) if the opportunity to do so is presented
to Stockholder on the proxy card, against any Alternative Transaction and (c)
not to revoke any such proxy.

     6.   NO SOLICITATION.  From and after the date hereof, the Stockholders
shall not, nor shall they permit any of their respective Subsidiaries to, nor
shall they authorize or permit any of their respective officers, directors,
members or employees to, and shall use their reasonable best efforts to cause
any investment banker, financial advisor, attorney, accountants or other
representatives retained by them or any of their respective Subsidiaries not
to, directly or indirectly through another person, (i) solicit, initiate or
encourage (including by way of furnishing information), or knowingly take any
other action designed to facilitate, any Alternative Transaction, or (ii)
participate in any discussions or negotiations regarding any Alternative
Transaction, provided that nothing herein shall affect the ability of any
Stockholder in its capacity as an officer, director, employee or advisor to
Powertel to take any action permissible under the DT Merger Agreement.

     7.   TERMINATION OF REGISTRATION RIGHTS.  The registration rights held by
the Stockholder pursuant to the Stock Purchase Agreement by and between
Powertel and the Stockholder dated March 4, 1996, and the rights/obligations
to purchase Shares pursuant to the Stock Purchase Agreement by and between the
Stockholder dated May 30, 2000, and Powertel


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<PAGE>   6
shall, in consideration of the undertakings by DT under this Agreement and the
DT Merger Agreement, be terminated and be of no further force or effect
effective at the Effective Time. The Stockholder agrees that (a) until the
earlier of (x) the later of January 1, 2001 and the date of the Powertel
Stockholders' Meeting, and (y) the termination of the DT Merger Agreement,
Stockholder shall not exercise any registration rights, (b) from the date hereof
until the earlier of the  termination of the DT Merger Agreement or the
Effective Time, Stockholder shall not be entitled to the benefit of any
preemption rights that Stockholder may have under the agreements listed in the
immediately preceding sentence and (c) if Powertel and DT agree to decrease the
exercise price of the Powertel Warrants in accordance with Article V of the
Powertel Warrant Agreement, Stockholder hereby waives any adjustment to the
Conversion Price (as defined in the Certificate of Designations governing the
Powertel Preferred Stock listed on Schedule A hereto) that it may have otherwise
been entitled to as a result of such decrease in the exercise price of the
Powertel Warrants. None of the agreements so listed shall be amended or modified
in a manner inconsistent with the terms of this Agreement without DT's prior
written approval.

     8.   ADDITIONAL SHARES AND ADDITIONAL RIGHTS. If, after the date hereof, a
Stockholder acquires record ownership or Beneficial Ownership of any additional
shares of capital stock of Powertel (any such shares, "ADDITIONAL SHARES"),
including, without limitation, upon exercise of any option, warrant or right
to acquire shares of capital stock of Powertel through the conversion of the
Powertel Preferred Stock or through any stock dividend or stock split, or
record ownership or Beneficial Ownership of any additional options, warrants or
rights to acquire shares of capital stock of Powertel (any such options,
warrants or rights, "ADDITIONAL RIGHTS"), the provisions of this Agreement
applicable to the Shares and the Rights shall be applicable to such Additional
Shares and Additional Rights from and after the date of acquisition thereof.
The provisions of the immediately preceding sentence shall be effective with
respect to Additional Shares or Additional Rights without action by any person
immediately upon the acquisition by any Stockholder of record ownership or
Beneficial Ownership of such Additional Shares or Additional Rights,
respectively.

     9.   CERTAIN AGREEMENTS WITH RESPECT TO THE PUT AGREEMENT BETWEEN POWERTEL
AND SONERA HOLDING, B.V., DATED MAY 30, 2000 (THE "SONERA PUT AGREEMENT").

     9.1  Effective as of the Effective Time, DT agrees to assume all
obligations of Powertel pursuant to the Sonera Put Agreement, including the
obligation to deliver to Sonera such shares of stock, securities or assets or
other consideration as Sonera may be entitled to acquire under the Sonera Put
Agreement. Sonera acknowledges and agrees that (i) the agreements of DT set
forth in this Section 9 are satisfactory in form and substance to Sonera and
satisfy those obligations of Powertel required to be satisfied prior to the
Effective Time, which arise under the Sonera Put Agreement due to the Merger's
constituting a change of control transaction under the Put Agreement.

     9.2  To the extent any DT Ordinary Shares are issuable to Sonera upon
exercise of its rights under the Sonera Put Agreement, such shares shall be
issued to the Eliska Partners Shares Trust in accordance with Annex 1.05(i) of
the Merger Agreement. Sonera shall accept issuance of DT Ordinary Shares by the
Eliska Partners Shares Trust in accordance with Annex 1.05(i) upon exercise of
is put rights for such shares. DT and Sonera acknowledge and agree that the
consideration to be issued to Sonera upon an exercise of its rights under the
Put Agreement does not constitute merger consideration pursuant to the Merger
Agreement.

     10.  MISCELLANEOUS.


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     10.1  ENTIRE AGREEMENT.  This Agreement constitutes the entire agreement
among the parties with respect to the subject matter hereof and, except for the
Stockholders Agreements as defined in the VoiceStream Reorganization Agreement
and the Stockholders Agreements as defined in the VoiceStream/DT Merger
Agreement, supersedes all other prior agreements and understanding, both
written and oral, among the parties hereto with respect to the Transfer or
voting of Shares. This Agreement is not intended to confer upon any Person
other than the parties hereto any rights or remedies hereunder.

     10.2  COSTS AND EXPENSES.  All costs and expenses incurred in connection
with this Agreement and the transactions contemplated hereby shall be paid by
the party incurring such expenses.

     10.3  INVALID PROVISIONS.  If any provision of this Agreement shall be
invalid or unenforceable under applicable law, such provision shall be
ineffective to the extent of such invalidity or unenforceability only, without
it affecting the remaining provisions of this Agreement.

     10.4  EXECUTION IN COUNTERPARTS.  This Agreement may be executed in
counterparts each of which shall be an original with the same effect as if the
signatures hereto and thereto were upon the same instrument. The obligations of
the Stockholders hereunder are several and not joint and the covenants and
agreements of the Stockholders herein are made only in their capacity as
stockholders of Powertel and not in any other capacity (including as directors
or officers of Powertel).

     10.5  SPECIFIC PERFORMANCE.  Stockholder agrees with DT as to itself that
if for any reason any Stockholder fails to perform any of its agreements or
obligations under this Agreement, irreparable harm or injury to DT would be
caused as to which money damages would not be an adequate remedy. Accordingly,
Stockholder agrees that, in seeking to enforce this Agreement against
Stockholder, DT shall be entitled, in addition to any other remedy available at
law, equity or otherwise, to specific performance and injunctive and other
equitable relief. The provisions of this SECTION 10.5 are without prejudice to
any other rights or remedies, whether at law or in equity, that DT may have
against Stockholder for any failure to perform any of its agreements or
obligations under this Agreement.

     10.6  AMENDMENTS; TERMINATION.

     (a)  This Agreement may not be modified, amended, altered or supplemented,
except upon the execution and delivery of a written agreement executed by the
parties hereto.

     (b)  The provisions of this Agreement (other than Sections 3, 4 and 5)
shall terminate upon the earliest to occur of (i) the Effective Time, (ii) the
date that is two (2) years after the date hereof, and (iii) the termination of
the DT Merger Agreement. The provisions of Sections 3.2 through 3.5 of this
Agreement shall terminate when the applicable time periods set forth therein
lapse, the remaining provisions of Section 3 of this Agreement shall terminate
when each of Sections 3.2 through 3.5 of this Agreement have terminated and the
provisions of Section 4 and Section 5 of this Agreement shall terminate upon
the earlier to occur of the Effective Time and the termination of the DT Merger
Agreement.

     10.7  GOVERNING LAW; SUBMISSION AND JURISDICTION.

     (a)  This Agreement shall be governed by and construed in accordance with
the laws of the State of Delaware without giving effect to the principles of
conflicts of laws thereof.

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<PAGE>   8
     (b)  Each of the parties hereof irrevocably agrees that any legal action or
proceeding with respect to this Agreement or for recognition and enforcement of
any judgment in respect hereof brought by the other party hereto or its
successors or assigns shall be brought and determined only in the United States
District Court for the State of Delaware or, in the event (but only in the
event) that such court does not have subject matter jurisdiction over such
action or proceeding in the courts of the State of Delaware. Each of the
parties hereto hereby irrevocable submits with regard to any such action or
proceeding for itself and in respect to its property, generally and
unconditionally, to the personal jurisdiction of the aforesaid courts. Each of
the parties hereto hereby irrevocably waives, and agrees not to assert, by way
of motion, as a defense, counterclaim or otherwise, in any action or proceeding
with respect to this Agreement, (i) any claim that it is not personally subject
to the jurisdiction of the above-named courts for any reason other than
the failure to serve in accordance with this SECTION 10.7(b) or that it or its
property is exempt or immune from jurisdiction of any such court or from any
legal process commenced in such courts (whether through service of notice,
attachment prior to judgment, attachment in aid of execution of judgment,
execution of judgment or otherwise), and (ii) to the fullest extent permitted
by the applicable law, that (x) the suit, action or proceeding in such court is
brought in an inconvenient forum, (y) the venue of such suit, action or
proceeding is improper and (z) this Agreement, or the subject matter hereof,
may not be enforced in or by such courts. Without limiting the foregoing, each
party agrees that service of process on such party as provided in SECTION 9.9
shall be deemed effective service of process on such party.

     10.8 Successors and Assigns. The provisions of this Agreement shall be
binding upon and inure to the benefit of the parties hereto and their
respective legal successors (including, in the case of Stockholder or any other
individual, any executors, administrators, estates, legal representatives and
heirs of Stockholder or such individual) and permitted assigns; provided that,
except as otherwise provided in this Agreement, no party may assign, delegate
or otherwise transfer any of its rights or obligations under this Agreement.

     10.9 Notices. 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 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):

     (a)  if to Stockholder, at Stockholder's address appearing on Schedule A
hereto or at any other address that Stockholder may have provided in writing
to DT.

     (b)  if to DT:

               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


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<PAGE>   9


                           Attention: Robert P. Davis
                           Facsimile: (212) 225-3999

     10.10 WAIVER OF IMMUNITY. Stockholder and DT each agree that, to the extent
that it or any of its property is or becomes entitled at any time to any
immunity on the grounds of sovereignty or otherwise based upon its status as an
agency or instrumentality of government from any legal action, suit or
proceeding or from setoff or counterclaim relating to this Agreement from the
jurisdiction of any competent court, from service of process, from attachment
prior to judgment, from attachment in aid of execution of a judgment, from
execution pursuant to a judgment or arbitral award, or from any other legal
process in any jurisdiction, it, for itself and its property expressly,
irrevocably and unconditionally waives, and agrees not to plead or claim, any
such immunity with respect to such matters arising with respect to this
Agreement or the subject matter hereof (including any obligation for the payment
of money). Stockholder and DT each agree that the waiver in this provision is
irrevocable and is not subject to withdrawal in any jurisdiction or under any
statute, including the Foreign Sovereign Immunities Act, 28 U.S.C. Section 1602
ET SEQ. The foregoing waiver shall constitute a present waiver of immunity at
any time any action is initiated against Stockholder or DT with respect to this
Agreement.



     IN WITNESS WHEREOF, the parties hereto have executed this Stockholder
Agreement as of the date first written above.

                                        DEUTSCHE TELECOM AG


                                        By:__________________________________
                                        Name:   Kevin Copp
                                        Title:  Head of International
                                                Legal Affairs


                                        SONERA CORPORATION


                                        By:__________________________________

                                        Name:   _____________________________

                                        Title:  _____________________________


                                        SONERA HOLDING, B.V.


                                        By:__________________________________

                                        Name:   _____________________________

                                        Title:  _____________________________





                                       9

<PAGE>   10

                                   SCHEDULE A

<TABLE>
<CAPTION>
Stockholder Name and                                 Number and Description of
      Address           Number of Existing Shares         Existing Rights
--------------------    -------------------------    -------------------------
<S>                     <C>                          <C>
Sonera Corporation.     100,000 Powertel Series A    4,626,744 shares of
</TABLE>



<TABLE>
<CAPTION>
Stockholder Name and                                 Number and Description of
      Address           Number of Existing Shares         Existing Rights
--------------------    -------------------------    -------------------------
<S>                     <C>                          <C>
P.O. Box 106            Preferred Stock              Powertel Common Stock
FIN-00051-TELE                                       currently issuable upon
Teollisuuskatu 15,                                   conversion of Powertel
Helsinki, Finland                                    Series A Preferred Stock
Attn: Kaj-Erik Relander,
Executive Vice President
Facsimile: 011 358 2040
3770

Sonera Holding, B.V.                                 Right/Obligation to
P.O. Box 106                                         purchase 1,740,947 shares
FIN-00051-TELE                                       of Powertel Common Stock
Teollisuuskatu 15,                                   pursuant and subject to
Helsinki, Finland                                    the Stock Purchase
Attn: Kaj-Erik Relander,                             Agreement dated May 30,
Executive Vice President                             2000, and 1,044,568
Facsimile: 011 358 2040                              shares of Powertel Common
3770                                                 Stock pursuant and
                                                     subject to the Put
                                                     Agreement dated May 30,
                                                     2000
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