Exhibit 99.2

                              AGREEMENT TO BE BOUND

                        BY VOICESTREAM INVESTOR AGREEMENT

         The undersigned, TDSI Corporation,  being the transferee from Telephone
and Data Systems,  Inc.  ("TDS") of 35,570,493  shares of the common stock,  par
value  $.001  per  share,  of  VoiceStream  Wireless  Corporation,   a  Delaware
corporation  (the  "Company"),  as a condition  to the  receipt of such  shares,
acknowledges that matters pertaining to the ownership of such shares is governed
by the Investor  Agreement dated as of May 4, 2000,  between the Company and TDS
(the  "Agreement"),  and  hereby  (1)  acknowledges  receipt  of a  copy  of the
Agreement,  and (2) agrees to be bound, to the same extent as TDS has heretofore
been  bound,  by the  terms  of the  Agreement,  as the  same has been or may be
amended from time to time.

                  Agreed to this 27th day of December, 2000.

                                       TDSI CORPORATION


                                       By:      /s/ LeRoy T. Carlson, Jr.
                                                --------------------------------
                                                Name:    LeRoy T. Carlson, Jr.
                                                Title:   President


                  Address for notice:

                           TDSI Corporation
                           c/o Telephone and Data Systems, Inc.
                           30 North LaSalle, Suite 4000
                           Chicago, Illinois  60602
                           Attn:  Chairman
                           Telecopy No.:  312-630-9299

                  with a copy to:

                           Sidley & Austin
                           One First National Plaza
                           Chicago, Illinois  60603
                           Attn:  Michael G. Hron, Esq.
                           Telecopy No.:  312-853-7036