<PAGE>   1
                                                                    EXHIBIT 10.1


                     SEVERANCE AND REIMBURSEMENT AGREEMENT

     This Agreement, entered into as of September 12, 1997, is between PageMart
Wireless, Inc., a Delaware corporation (the "Employer"), and N. Ross Buckenham
(the "Employee").

     The Employer has offered Employee the position of President, and has
requested Employee to move his residence to Dallas, Texas. Employee is willing
to accept such position and move his residence upon the terms and conditions
set forth in this Agreement.

     THEREFORE, the parties hereby agree as follows:

     1.   SEVERANCE. If the Employer's employment of Employee terminates for
          any reason other than an Excluded Reason (as defined below) or the
          death or disability of Employee, then the Employer will pay Employee
          an amount equal to one-half of his annual base salary in effect at the
          date of termination. Such amount shall be paid within 10 days after
          the date of termination of employment and shall be subject to
          withholding taxes to the extent required by law.

     2.   REIMBURSEMENT. If the Employer's employment of Employee terminates
          for any reason other than an Excluded Reason (as defined below), and
          if Employee moves his principal residence to another location outside
          of Texas within two years after the date of termination of employment,
          then the Employer will pay the Employee $100,000 to compensate the
          Employee for the expenses of moving his principal residence. Such
          amount shall be paid within 10 days after Employee provides the
          Employer with evidence that he has moved his principal residence and
          shall be subject to withholding taxes to the extent required by law.

     3.   EXCLUDED REASONS. As used in this Agreement:

          (a)  The term "Excluded Reason" means the following:

               (i)  The retirement, resignation or other voluntary termination
                    of employment by the Employee for any reason other than a
                    Good Reason (as defined below); or
<PAGE>   2
               (ii) The termination of employment by Employer due to conduct by
                    Employee constituting (i) fraud; (ii) misappropriation of
                    the Employer's property; (iii) an act of moral turpitude; or
                    (iv) a willful violation of any law, rule or regulation or
                    causing the Employer to willfully violate any law, rule or
                    regulation.
                        
          (b)  The term "Good Reason" means that Employee is required to accept
               a decrease in his base salary or a demotion to a position that is
               subordinate to the position of President. To qualify as a
               termination of employment for Good Reason, Employee must deliver
               to the Employer written notice of termination for Good Reason
               within 30 days after the event constituting Good Reason, in which
               event his employment will terminate 10 days after the date of the
               notice.

     4.   Conditions. The Employer's obligation to pay Employee the amounts set
          forth in Sections 1 and 2 of this Agreement are subject to the
          Employer's receipt of a general release of claims against the Employer
          executed by Employee in a form satisfactory to the Employer. The time
          of payment in each case shall be extended, if necessary, to the date
          on which such release cannot be terminated or revoked by the Employee
          pursuant to the terms of such release or applicable law.

     5.   Effective Date and term. This Agreement shall become effective after
          Employee has moved his principal residence to Dallas, Texas, and shall
          terminate on the fifth anniversary of the date hereof.

     6.   Miscellaneous. This Agreement is not intended to be an employment
          agreement providing for any express or implied term of employment.
          This Agreement represents the entire agreement between the parties
          with respect to the subject matter hereof, and all prior agreements
          between the parties relating to that subject matter are superceded. No
          modification or amendment of this Agreement shall be valid and
          binding, unless it is in writing and signed by the party against whom
          enforcement is sought. The waiver of any provision of this Agreement
          shall be effective only if in writing and signed by the party against
          whom enforcement is sought, and then only in the specific instance and
          for the particular purpose for which it was given. This Agreement
          shall be binding upon the Employee and his heirs and personal
          representatives, and upon the Employer and it's successors and
          assigns. Neither this Agreement, nor any rights and obligations
          created under it, may be assigned by the Employee without the prior
          written consent of the Employer. This Agreement shall be construed in
          accordance with, and governed by, the laws of the State of Texas.


Severance and Reimbursement Agreement                                     Page 2

<PAGE>   3
Executed as of the date first written above.

                                                /s/ N. ROSS BUCKENHAM
                                                ------------------------------
                                                N. Ross Buckenham


                                                PAGEMART WIRELESS, INC.


                                                By: /s/ JOHN D. BELETIC
                                                    ---------------------------
                                                    Title: President & CEO




Severance and Reimbursement Agreement                                    Page 3