<PAGE>   1

                                                                   EXHIBIT 10.3

                          SECOND AMENDED AND RESTATED
                   SATELLITE SERVICES SUPPLEMENTAL AGREEMENT


         THIS SECOND AMENDED AND RESTATED SATELLITE SERVICES SUPPLEMENTAL
AGREEMENT (this "Agreement") is made and entered into as of July 1, 1998 (the
"Execution Date") by and between AvData Systems, Inc., a Delaware corporation
("AvData"), whose principal place of business is located at 55 Marietta Street,
NW, Atlanta, Georgia 30303, and PageMart Wireless, Inc., a Delaware corporation
(the "Customer" or "PageMart") with offices at 3333 Lee Parkway, Suite 100,
Dallas, Texas 75219.

                                    RECITALS

         WHEREAS, AvData and PageMart, Inc. are parties to an Amended and
Restated Satellite Services Supplemental Agreement, dated as of December 18,
1997 (the "Existing SSS Agreement"), concerning the purchase of certain
satellite services;

         WHEREAS, Customer and AvData have entered into an Amended and Restated
Master Agreement dated December 18, 1997 ("Master Agreement");

         WHEREAS, this Agreement is independent of the Master Agreement, and
all of the parties' rights and obligations hereunder shall continue in full
force and effect notwithstanding any termination of, or default by either party
under, the Master Agreement;

         WHEREAS, as a result of a Satellite Capacity Failure, the Satellite
Capacity with respect to the Galaxy IV Satellite was terminated pursuant to
Section K.1.a of the Existing Agreement;

         WHEREAS, AvData continues to lease certain Ku-band satellite
transponder capacity on GE-1, a satellite operated by GE Americom
Communications, Inc. ("GE"), and has secured additional Ku-band transponder
capacity on other satellites operated by GE, and Customer desires to purchase
from AvData and AvData is willing to provide to Customer, a portion of such
satellite transponder capacity for use in the VNI Network; and

         WHEREAS, the parties desire to amend and restate the Existing SSS
Agreement to reflect the termination of capacity on Galaxy IV and the addition
of new capacity on satellites operated by GE.

                                   AGREEMENT

         NOW, THEREFORE, in consideration of the premises, and other good and
valuable consideration received and acknowledged, AvData and Customer agree as
follows:

         During the Satellite Services Term, AvData shall provide Customer's
Satellite Capacity in accordance with, and Customer shall be bound by, the
terms and conditions set forth below:

A.       SATELLITE SERVICES TERM:

1.       "Commencement Date": 12:00 a.m. (Eastern Time) on July 1, 1998.

2.       "Termination Date": 11:59 p.m. (Eastern Time) on July 31, 2003, unless
         earlier terminated pursuant to this Agreement.

B. CUSTOMER'S SATELLITE CAPACITY: AvData shall provide satellite transponder
capacity for the VNI Network according to the terms hereof. From the
Commencement Date through the Termination Date Customer's Satellite Capacity
shall be provided through Ku-band transponder capacity leased by AvData on
Satellite(s) in accordance with Schedule 1 attached hereto.

         C. PRICE: Customer shall pay to AvData a monthly satellite capacity
         payment for Customer's Satellite Capacity, in accordance with Section
         J below and Schedule 1 hereto. To the extent AvData receives credits
         from the Satellite Operator by reason of service interruption
         affecting the


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                          SECOND AMENDED AND RESTATED
                   SATELLITE SERVICES SUPPLEMENTAL AGREEMENT

         Satellite Capacity provided hereunder for a period of one (1) hour or
         more (measured from the AvData receives notice thereof from Customer),
         AvData agrees to promptly credit Customer with credits provided by the
         Satellite Operator for such interruption. The credit shall be equal to
         a pro rata portion (based on total bandwidth of the Satellite Capacity
         contracted for by Customer on the Satellite compared to total
         bandwidth of the Satellite Capacity contracted for by AvData for its
         own or third party use on the Satellite) of all amounts credited by
         the Satellite Operator to AvData with respect to any interruption in
         service. AvData will apply the credit promptly to any outstanding
         invoice between AvData and Customer under this Agreement or any other
         agreement between AvData and Customer, as selected by AvData in its
         sole discretion.


D. DEPOSIT: The parties acknowledge that Customer has previously paid AvData a
non-refundable satellite services deposit, which has been retained by AvData in
consideration for the modifications contained in the Existing SSS Agreement.
PageMart acknowledges that it is not entitled to a set-off against any
financial obligations with respect to such payment.

E.       CERTAIN DEFINITIONS

1.       "Affiliates" shall mean, with respect to any Person, any other Person
         directly or indirectly controlling, controlled by or under common
         control (i.e., the power to direct affairs by reason of ownership of
         voting stock, by contract or otherwise) with such Person and any
         member, director, officer or employee of such Person.

2.       "FCC" shall mean the Federal Communications Commission or any
         successor organization.

3.       "Satellite(s)" shall mean SN-4, G-3R and GE-1, through which AvData
         will provide Customer's Satellite Capacity.

4.       "Laws" shall mean all international, federal, state, local and other
         laws, rules and other regulations, including, without limitation,
         those issued by the FCC.

5.       "Person" shall mean any person or entity, whether an individual,
         trustee, corporation, general partnership, limited partnership, trust,
         unincorporated organization, business association, firm, joint
         venture, governmental agency or authority, or otherwise.

6.       "Transponder(s)" shall mean a component of the Satellite(s) which, for
         a particular frequency band, receives, amplifies, translates frequency
         and retransmits radio signals. Each Transponder contains one traveling
         wave tube amplifier (a "TWTA"). Transponder shall also mean, for
         purposes of this definition, any replacement or alternate components
         thereof.

7.       "Satellite Capacity Failure" shall mean the failure of AvData to
         provide Customer's aggregate Satellite Capacity on a Satellite(s) (due
         to a Satellite or Transponder failure, including relocation of orbital
         position by FCC order). Determination that a Satellite Capacity
         Failure has occurred shall be made by AvData in its sole discretion.

8.       "Usage" or "Use" shall refer to radio transmission to, or utilization
         of, the Satellite(s) for the VNI Network.

9.       "Satellite Operators" shall mean the owner(s) of the Satellite(s)
         specifically authorized by the FCC to operate the Satellite(s) and
         through whom AvData makes available the satellite capacity required
         for the VNI Network.

10.      "Primary Hub" shall mean the Equipment at AvData's primary hub
         location in Atlanta, Georgia which will be used to access Customer's
         Satellite Capacity to run the VNI Network.

11.      "Alternate Hub" shall mean the equipment PageMart sets up at a site to
         be determined which will be used to access Customer's Satellite
         Capacity to run the VNI Network for load sharing with, or failure of,
         the Primary Hub.

12.      "Customer's Satellite Capacity" shall mean the satellite capacity to
         be provided hereunder to Customer (expressed as SCUs or High Power
         SCUs) during the Satellite Services Term, as more particularly


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                          SECOND AMENDED AND RESTATED
                   SATELLITE SERVICES SUPPLEMENTAL AGREEMENT

         described in Paragraph J.2. hereof and Schedule 1 hereto. In addition,
         if PageMart requests additional satellite capacity as described in
         Schedule 1 hereto, subject to availability of such satellite capacity,
         such additional satellite capacity shall be included upon commencement
         of service for such satellite capacity.

13.      "Equipment" shall mean the Very Small Aperture Satellite Terminals
         (VSATs) and associated hub hardware and remote site hardware including
         embedded software provided by AvData under the Master Agreement.

14.      "Satellite Capacity Unit" or "SCU" - One SCU equals 800 kHz of
         bandwidth, which is normally configured as one (1) 128 Kbps outbound
         channel and two (2) 64 Kbps inbound channels. Using standard power
         levels and BPSK modulation, the percentage of available bandwidth in
         the transponder that is utilized by a SCU is equal to the percentage
         of the power available in the transponder utilized by that SCU.

15.      "High Power SCU" - One High Power SCU consumes twice the satellite
         capacity of one standard power SCU. Using high power levels and BPSK
         modulation, the percentage of available power in the transponder that
         is utilized by a High Power SCU is equal to two (2) times the
         percentage of available bandwidth in the transponder that is utilized
         by a SCU. A High Power SCU has a power density of not less than 9
         dBW/4KHz and requires authorization from the FCC.

16.      "VNI" or "VNI Network" shall mean the VSAT network infrastructure
         consisting of the Equipment and software provided by AvData under the
         Master Agreement.

17.      "GE-1 Satellite" shall mean a communications satellite owned and
         operated by GE and positioned at 103(Degree) west longitude orbital
         position.

18.      "SN-4 Satellite" shall mean a communications satellite owned and
         operated by GE and positioned at 101 degrees W. L. orbital position.
         All references herein to the SN-4 Satellite shall be deemed to refer
         to the GE-4 communications satellite currently scheduled to be
         launched into geostationary orbit by GE during the second quarter of
         1999 after AvData transitions its current capacity on SN-4 to GE-4.

19.      "G-3R Satellite" shall mean a communications satellite owned and
         operated by PanAmSat and positioned at 95(Degree) west longitude
         orbital position. G-3R may be preempted in the event of a Satellite
         Capacity Failure of Galaxy 7 or Galaxy 8 (satellites owned and
         operated by PanAmSat).

F.       CERTAIN UNDERSTANDINGS

         1. Ownership of Transponders. Customer understands and agrees that the
Satellite Operators are the FCC-authorized operators of the Satellites. Neither
this Agreement nor the provision of Customer's Satellite Capacity hereunder
shall, or shall be deemed to, convey title or any other ownership interest to
Customer in or to any Satellite, any Transponder or any part thereof. Customer
acknowledges and agrees (i) that nothing contained in this Agreement shall
prevent any sale, mortgage, or encumbrance of any Satellite or any Transponder
thereof by the owner, (ii) that Customer's Satellite Capacity is provided on a
right to use basis (with Equipment and services provided by AvData under the
Master Agreement) and is not being sold to Customer, and (iii) that neither any
Transponder nor any Satellite, nor any right to use thereof nor any interest of
any type therein, shall be subject to any claim, prior, subsequent or
otherwise, of Customer or its creditors as a result of this Agreement.
Notwithstanding the foregoing, AvData shall use reasonable efforts to provide
that the foregoing restrictions shall not impact or interfere with Customer's
use of Customer's Satellite Capacity as provided for herein.

         2. Control of Satellite. Customer understands and agrees that the
Satellite Operator(s) shall control and provide for the operation of the
Satellite(s).

         3. Communication with Satellite. All communications with the
Satellite(s) will be provided through Equipment controlled by AvData at either
the Primary Hub or Alternate Hub; provided, however, upon the prior written
request of Customer, AvData shall use its reasonable efforts to obtain the
consent of each Satellite Operator to permit Customer to exercise control of
the Equipment at the Alternate Hub, and


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                          SECOND AMENDED AND RESTATED
                   SATELLITE SERVICES SUPPLEMENTAL AGREEMENT

upon obtaining such consent(s), Customer shall have the right to make
communications with the Satellite(s) through Equipment controlled by Customer
or its nominee at the Alternate Hub.

G.       CONTINUITY OF SERVICE

         1. Preemption/Interruption of Service. Customer recognizes and agrees
with respect to each Satellite that for technical or safety reasons, which
shall include, but shall not be limited to, (1) the protection of the overall
health or performance of the Satellite or its Transponders; (2) the prevention
of interference or cross-talk; (3) the protection of public safety; or (4)
compliance with an order from the FCC or other governmental authorities - and
the existence of which the Satellite Operator shall determine in its sole
discretion - the Satellite Operator may take the following actions: (i) preempt
or interfere with Customer's Use of any Transponder or other component of the
Satellite, (ii) reassign TWTAs to different Transponders on the Satellite, or
(iii) reassign the frequency assignment of Customer's Satellite Capacity.
Customer acknowledges and agrees that any such action by Satellite Operator may
result in the preemption or interruption of the Use of Customer's Satellite
Capacity. AvData shall notify Customer as soon as reasonably practical after
receipt by AvData of oral or written notice from the Satellite Operator
concerning any such action and shall use reasonable efforts to cause the
Satellite Operator to schedule and conduct such action so as to minimize the
Satellite Operator disruption of Customer's Use of Customer's Satellite
Capacity. Customer acknowledges and agrees that if such preemption or
interruption occurs, then Customer shall cooperate with and assist AvData and
the Satellite Operator during such periods and Customer's sole remedies shall
be any credits provided pursuant to Section C herein and, in the case of a
Satellite Capacity Failure, the termination of this Agreement or reduction in
Customer's Satellite Capacity pursuant to Paragraph K herein.

         2. Provision of Continuing Service. In the event of a Satellite
Capacity Failure, AvData shall use its best efforts to cause the Satellite
Operator to provide Customer's Satellite Capacity using spare Transponder
capacity on the Satellite, if available, or if such spare capacity is
unavailable, then by using an alternate Transponder on the Satellite of the
same polarity, if available. The availability of such spare or alternate
Transponder on the Satellite, on a permanent or temporary basis, shall be
determined by the Satellite Operator in its sole discretion. The foregoing
notwithstanding, Customer's sole remedies for any preemption of Use shall be
any credits provided pursuant to Section C herein and, in the case of a
Satellite Capacity Failure, the termination of this Agreement or reduction in
Customer's Satellite Capacity pursuant to Paragraph K herein.


H.       CUSTOMER'S OBLIGATIONS

         1. Compliance With Agreement and Laws. During the Satellite Services
Term, Customer shall comply with the terms of this Agreement and shall be
responsible for complying with, and shall comply with all Laws applicable to it
regarding the operation and Use of the Satellites and the Transponders and
regarding Use of Customer's Satellite Capacity. Customer shall be permitted to
use Customer's Satellite Capacity for any business unit, subsidiary, Strategic
Alliance Partner or customer of PageMart subject to the approval of AvData,
which shall not be unreasonably withheld, provided, however, operation of the
Equipment provided under the Master Agreement or any other equipment used to
access Customer's Satellite Capacity, including PageMart's Alternate Hub, must
be in strict accordance with guidelines and instructions provided by the
Satellite Operator directly or through AvData.

I.       REMEDIES

         1. Limitation of Liability

         a. ANY AND ALL EXPRESS AND IMPLIED WARRANTIES INCLUDING, BUT NOT
LIMITED TO, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PURPOSE OR USE,
ARE EXPRESSLY EXCLUDED AND DISCLAIMED BY AVDATA. CUSTOMER EXPRESSLY AGREES THAT
AVDATA'S SOLE OBLIGATIONS AND CUSTOMER'S EXCLUSIVE REMEDIES FOR ANY CAUSE
WHATSOEVER (INCLUDING, WITHOUT LIMITATION, LIABILITY ARISING


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                          SECOND AMENDED AND RESTATED
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FROM NEGLIGENCE) ARISING OUT OF OR RELATING TO THIS AGREEMENT AND/OR THE
TRANSACTIONS CONTEMPLATED HEREBY AND THEREBY ARE LIMITED TO TERMINATION OF THIS
AGREEMENT FOR THE REASONS DESCRIBED IN PARAGRAPH G ABOVE, AND ALL OTHER
REMEDIES OF ANY KIND ARE EXPRESSLY EXCLUDED.

         b. IN NO EVENT SHALL AVDATA BE LIABLE FOR ANY INCIDENTAL OR
CONSEQUENTIAL DAMAGES, WHETHER FORESEEABLE OR NOT, OCCASIONED BY ANY DEFECT IN
CUSTOMER'S SATELLITE CAPACITY, FAILURE OF THE CUSTOMER'S SATELLITE CAPACITY TO
PERFORM OR ANY OTHER CAUSE WHATSOEVER. AVDATA MAKES NO WARRANTY, EXPRESS OR
IMPLIED, TO ANY OTHER PERSON CONCERNING CUSTOMER'S SATELLITE CAPACITY AND
CUSTOMER SHALL INDEMNIFY AVDATA FROM ANY CLAIMS MADE UNDER ANY WARRANTY OR
REPRESENTATION BY CUSTOMER TO ANY THIRD PARTY.

         2. Indemnification. Customer shall indemnify and save AvData and the
Satellite Operators harmless from all liability disclaimed by AvData, as
specified above, to the extent such liability arises in connection with the
provision by AvData or the Satellite Operators of facilities and/or Customer's
Satellite Capacity or use of Customer's Satellite Capacity pursuant to this
Agreement provided, however, Customer shall not be obligated to indemnify
AvData from such liability to the extent such liability arises from the willful
misconduct or gross negligence of AvData.

J.       PAYMENTS TO AVDATA

         1. Payment.

         a. Unless otherwise provided, any sum due AvData for the provision of
Customer's Satellite Capacity shall be invoiced and payable in advance on the
first day of each month.

         b. If any payment of any sum due from Customer is not received by
AvData within thirty (30) days after such payment is due, then such overdue
amount shall be subject to a delinquency charge at the rate of interest equal
to one and one-half percent (1 1/2%) per month, from the date such overdue
amount was actually due until the date it is actually received by AvData.

         c. Customer's obligations to make the monthly satellite capacity
payments provided by Paragraph C above and J(2) below shall be absolute and
unconditional and shall not be affected by any circumstances, including,
without limitation, any setoff, counterclaim, recoupment, defense or other
right which Customer may have against AvData or anyone else for any reason
whatsoever.

         d. The charges specified herein do not include any amounts for sales,
use, property, privilege, license, excise or similar taxes, fees or assessments
which may be levied by any governmental agency on this Agreement, the services
provided or the payments made hereunder. Any such taxes or charges shall be
paid directly by Customer to the taxing authority, if legally permitted.
Otherwise, if required to be paid by AvData, the amount shall be reimbursed to
AvData by the Customer. Upon request, the Customer shall provide AvData with
tax exemption certificates, if applicable, or evidence of tax payments, if made
by Customer.

2.       Required Satellite Capacity.

         a. Commencing July 1, 1998, PageMart shall pay [*] per month per
Satellite Capacity Unit ("SCU") for satellite capacity on GE-1 Satellite and
[*] per month per SCU for satellite capacity on SN-4 Satellite in accordance
with Schedule 1 hereto. PageMart shall have the right to designate by written
notice by PageMart that a portion of Customer's Satellite Capacity, not to
exceed [*] SCUs (i.e., [*] High Power SCUs) on either GE-1 or SN-4, shall be
provided as High Power SCUs. The provision of Customer's Satellite Capacity as
High Power SCUs on either GE-1 or SN-4 shall be subject to availability of High
Power SCUs on the Satellite(s) and regulatory approval by the FCC. Upon receipt
of such written


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                          SECOND AMENDED AND RESTATED
                   SATELLITE SERVICES SUPPLEMENTAL AGREEMENT

notice, AvData shall pursue such regulatory approval on a "best efforts" basis,
at PageMart's sole cost and expense. One (1) High Power SCU shall count as two
(2) SCUs for the purpose of the above calculations.

         b. AvData shall use commercially reasonable efforts to resell any SCUs
(in increments of 1/4 SCUs, or 200 kHz) that PageMart specifies in writing to
AvData to resell; provided, however, that PageMart in such written notice
irrevocably releases the SCUs for the duration of this SSS Agreement. PageMart
shall be required to continue to pay for the SCUs until such time, if any, as
AvData is able to resell the SCUs, as set forth below in Paragraph J(2)(c).

         c. AvData shall reduce PageMart's minimum monthly payments in the
amount of [*] for each [*] SCU that AvData resells on GE-1or [*] for each [*]
SCU that AvData resells on SN-4; provided, however, that AvData resells such
SCU at a rate equal or greater than [*] per [*] SCU that AvData resells on
GE-1or [*] for each [*] SCU that AvData resells on SN-4. AvData shall be
permitted to receive payments for such resold SCUs directly from the purchaser.

         d. AvData further agrees not to purchase additional satellite capacity
for its own use from the time that PageMart gives AvData written notice of
released satellite capacity pursuant to Paragraph J(2)(b) above if AvData
determines, in its reasonable discretion, that AvData's satellite capacity
needs can be reasonably satisfied from PageMart's released satellite capacity,
and in such event AvData shall reduce PageMart's minimum monthly payments for
satellite capacity by [*] for each [*] SCU that AvData that uses on GE-1or [*]
for each [*] SCU that AvData uses on SN-4.

K.       TERMINATION

         1. Events of Termination. This Agreement shall terminate automatically
upon the Termination Date, unless terminated earlier pursuant to one of the
following paragraphs:

         a. Termination for Satellite Capacity Failure. If a Satellite Capacity
Failure continues uninterrupted for more than five (5) consecutive days, or
such other period is mutually agreed upon in writing by AvData and Customer,
then this Agreement may be immediately terminated by either party by written
notice to the other delivered on or before the thirtieth day after the calendar
day on which the Satellite Capacity Failure began; provided, however, that if
such Satellite Capacity Failure affects only one Satellite and a portion of
Customer's Satellite Capacity remains available from other Satellite(s), then
the right of termination shall apply only to Customer's Satellite Capacity
received hereunder from such failed Satellite and this Agreement shall continue
in force with respect to the remaining portion of Customer's Satellite
Capacity. If so terminated, AvData shall refund to Customer the amount of any
prepaid monthly charges for the terminated capacity prorated from the date of
the Satellite Capacity Failure, and AvData shall have no other or further
liability to Customer.

         b. Cancellation for Non-Payment and Violations of Law. Notwithstanding
anything to the contrary and in addition to all other remedies AvData may have,
AvData may immediately cancel this Agreement and accelerate all remaining
payments due through July 31, 2003 if Customer materially breaches any
provision of this Agreement, including for example (but without limitation),
(1) if Customer fails to pay when due any amounts due pursuant to this
Agreement within ten (10) days after AvData has delivered notice to Customer of
such non-payment, or (2) if Customer violates the provisions of Paragraph H.1.
("Compliance with Laws"). Upon termination, pursuant to this Paragraph K.1.b,
AvData shall be entitled to transfer Customer's Satellite Capacity immediately
to whomever AvData sees fit, Customer shall not be entitled to any equitable
relief as a result thereof, and Customer's exclusive remedy shall be limited to
recovery of any payments made by it to AvData for the period of time as to
which it has been canceled, without interest, less any claim AvData has against
Customer by reason of such Customer's default.

         c. Termination by Customer. In event that AvData fails to provide
Customer's Satellite Capacity to Customer as a result of the termination by a
Satellite Operator of the lease to AvData of Ku-Band satellite transponder
capacity due to a default by AvData, Customer, provided that Customer is not in
default hereunder, shall have the right to reduce Customer's Satellite Capacity
under this Agreement to the extent of the Customer's Satellite Capacity
received hereunder from such Satellite Operator if AvData fails to cure such
failure within thirty (30) days after receiving written notice of such failure
from Customer. If


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                          SECOND AMENDED AND RESTATED
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Customer's Satellite Capacity is so reduced, AvData shall (i) refund to
Customer the amount of any prepaid monthly charges for the terminated
Customer's Satellite Capacity prorated from the date AvData failed to provide
such Customer's Satellite Capacity and (ii) provide reasonable cooperation, at
Customer's request and expense, with any efforts by Customer to contract
directly with the Satellite Operator for such terminated Customer's Satellite
Capacity, and AvData shall have no other or further liability to Customer with
respect to such terminated Customer's Satellite Capacity.

         2. Continuation after Termination of Master Agreement. The parties
acknowledge and agree that this Agreement is a separate, free standing contract
and is independent of the Master Agreement. This Agreement, and the parties
rights and obligations hereunder, shall continue in full force and effect
notwithstanding any termination of, or default by either party under, the
Master Agreement.


L.       MISCELLANEOUS

         1. Headings. The Paragraph headings used in this Agreement, except
where terms are specifically defined, are for reference and convenience only
and shall not enter into the interpretation hereof.

         2. Waiver. No delay or omission by either party to exercise any right
or power shall impair any such right or power or be construed to be a waiver
thereof. A waiver by either of the parties of any of the covenants, conditions
or agreements to be performed by the other or any breach thereof shall not be
construed to be a waiver of any succeeding breach thereof or of any other
covenant, condition or agreement herein contained.

         3. Severability. If, but only to the extent that, any provision of
this Agreement is declared or found to be illegal, unenforceable or void, then
both parties shall be relieved of all obligations arising under such provision,
it being the intent and agreement of the parties that this Agreement shall be
deemed amended by modifying such provision to the extent necessary to make it
legal and enforceable while preserving its intent. If that is not possible,
another provision that is legal and enforceable and achieves substantially the
same objective shall be substituted. If the remainder of this Agreement is not
affected by such declaration or finding and is capable of substantial
performance then the remainder shall be enforced to the extent permitted by
law.

         4. Relationship of Parties. AvData is performing pursuant to this
Agreement only as an independent contractor and nothing set forth in this
Agreement shall be construed to create the relationship of principal and agent
between AvData and Customer. Neither AvData nor Customer shall act or attempt
to act or represent itself, directly or by implication, as an agent of the
other party or its Affiliates or in any manner assume or create, or attempt to
assume or create, any obligation on behalf of, or in the name of, the other
party or its Affiliates.

         5. Approvals and Authorizations. The obligations of the parties hereto
shall be subject to obtaining and maintaining all necessary regulatory and
other governmental approvals and authorizations. The parties agree to use their
respective and, where applicable, collective best reasonable efforts to obtain
promptly and maintain any such approvals.

         6. Notices. In addition to such other requirements as may be set forth
herein, any notices hereunder by one party to the other party shall be given in
writing by personal delivery (or by recognized overnight delivery service) or
posted by certified mail return receipt requested, to the parties at the
following addresses:

         IF AVDATA, SEND TO:                  IF CUSTOMER, SEND TO:
         AvData Systems, Inc.                 PageMart Wireless, Inc.
         55 Marietta Street                   3333 Lee Parkway, Suite 100
         Atlanta, GA  30303                   Dallas, TX   75219

         Attn:  Judith H. Drobinski           Attn:  James E. Freytag
         V.P. - Finance & Admin.              Director of Network Implementation


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                          SECOND AMENDED AND RESTATED
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Notices will be deemed to have been given hereunder when delivered (whether or
not accepted by the addressee).

         7. Confidentiality. Each party hereby agrees that all non-public,
confidential or proprietary information communicated to it by the other party
or its customers, whether before or after the Execution Date, shall be and was
received in strict confidence, shall be used only for purposes of this
Agreement, and, for a period of five (5) years following the termination of
this Agreement, shall not be disclosed by such party, its agents or employees
without the prior written consent of the other party, except as may be
necessary by reason of legal, accounting or regulatory requirements beyond the
reasonable control of the disclosing party. The obligations set forth in this
Section shall survive termination of this Agreement.

         8. Force Majeure. The term "Force Majeure" shall include, but not be
limited to, fires or other casualties or accidents, acts of God, severe weather
conditions, sun outages, strikes or labor disputes, war or other violence, any
law, order, proclamation, regulation, ordinance, demand or requirement of any
governmental agency or any other act or condition whatsoever beyond the
reasonable control of the affected party. A party whose performance of its
obligations hereunder is prevented, restricted or interfered with by reason of
a Force Majeure condition shall be excused from such performance to the extent
of such Force Majeure condition so long as such party immediately continues
performance whenever and to the extent such causes are removed. Nothing in this
Section shall relieve Customer of its obligations to make payments to AvData in
accordance with Paragraphs C and J of this Agreement, except to the extent that
AvData is relieved of its obligations to make payments to the Satellite
Operator by such Force Majeure condition.

         9. Applicable Law and Entire Agreement. This Agreement shall be
interpreted, construed and governed in accordance with the laws of the State of
Georgia. This Agreement constitutes the entire agreement between the parties,
supersedes all previous understandings, commitments or representations and is
intended as the complete and exclusive statement of the terms of the agreement
between the parties concerning the subject matter hereof. This Agreement may
not be amended or modified in any way, and none of its provisions may be
waived, except by a writing signed by each party hereto.

         10. Attorney's Fees. In the event of any dispute or controversy
arising hereunder, any court having jurisdiction in any such dispute or
controversy shall determine which of the parties is the prevailing party and
shall award to the prevailing party the reasonable fees and expenses of
counsel, experts and other court costs incurred in connection with such dispute
or controversy.

         11. No right of Transfer. Customer shall not, and shall not have the
right to, grant, sell, assign, encumber, permit the utilization of, license,
lease, or otherwise convey, directly or indirectly, in whole or in part
(individually, a "Transfer"), Customer's Satellite Capacity, or any of its
rights under this Agreement, to any other entity or person. Notwithstanding the
foregoing, Customer may assign its Satellite Capacity, and its rights under
this Agreement, without AvData's written consent, to any corporation,
partnership or other entity which is controlled by Customer and in which
Customer has not less than fifty-one percent (51%) of the ownership interest,
provided that no such assignment shall relieve Customer of any of its
obligations hereunder.

         12. Successors and Assigns. Subject to Paragraph L.11 above, this
Agreement shall be binding on and shall inure to the benefit of any successors
and assigns of the parties, provided that no assignment of this Agreement shall
relieve either party hereto of its obligations to the other party. Any
purported assignment by either party not in compliance with the provisions of
this Agreement shall be null and void and of no force and effect.


--------------------------------------------------------------------------------

            Second Amended and Restated Satellite Services Agreement
Page 8                AvData Systems, Inc - Proprietary

<PAGE>   9

                          SECOND AMENDED AND RESTATED
                   SATELLITE SERVICES SUPPLEMENTAL AGREEMENT


         IN WITNESS WHEREOF, each of the parties hereto has caused this
Agreement to be duly executed on its behalf by an officer thereunto duly
authorized, all as of the day and year first above written.


                                   AVDATA SYSTEMS, INC.



                                    By: /s/ HAROLD E. COWAN
                                      ------------------------------------------
                                    Title: Vice President Account Management
                                          --------------------------------------
                                    Date: 9/25/98
                                         ---------------------------------------
                                    Signed: Harold E. Cowan
                                           -------------------------------------

                                    PAGEMART WIRELESS, INC.



                                    By: /s/ JACK D. HANSON
                                      ------------------------------------------
                                    Title: VP Network Operation
                                          --------------------------------------
                                    Date: 9/24/98
                                         ---------------------------------------
                                    Signed: Jack D. Hanson
                                           -------------------------------------


            Second Amended and Restated Satellite Services Agreement
Page 9                AvData Systems, Inc - Proprietary


<PAGE>   10


                          SECOND AMENDED AND RESTATED
                   SATELLITE SERVICES SUPPLEMENTAL AGREEMENT


                                   SCHEDULE 1

                           MONTHLY RECURRING CHARGES

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------
   SATELLITE       SCU QUANTITY #          UNIT PRICE           EXTENDED PRICE
-------------------------------------------------------------------------------
  <S>              <C>                     <C>                  <C>
     GE-1             [*]                     [*]                   [*]
-------------------------------------------------------------------------------

   SN-4/GE-4          [*]                     [*]                   [*]
-------------------------------------------------------------------------------
#        - Satellite Capacity Unit (SCU) represents one (1) 128 Kbps outbound
         channel and two (2) 64 Kbps inbound channels which equate to 800 kHz
         of satellite capacity per SCU.
-------------------------------------------------------------------------------
</TABLE>



CONDITIONS TO PRICING

Satellite Capacity Unit charges will begin at [*] on GE-1 at [*] per SCU/month
and [*] SCU's on SN-4 at [*] per SCU/month. Effective August 1, 1998, the SCU
total on GE-1 will increase to [*] at [*] per SCU/month. Thereafter, a total of
[*] SCUs per month shall be purchased until July 31, 2003, when the [*] SCU's on
GE-1 shall terminate.


SATELLITE(S)

As of the Execution Date, AvData has commitments to provide PageMart [*] SCU's
on GE-1 and [*] SCUs on SN-4. Provisioning of a High Power SCU option on either
GE-1 or SN-4, if requested by PageMart, is subject to the approval of both the
Satellite Operator and the FCC.

Regarding the planned replacement of SN-4 with GE-4, the following additional
qualifications apply:

         (a)      Satellite Operator is planning for GE-4 to be launched in the
                  second quarter of 1999, and to become "Commercially
                  Operational" (date when GE-4 is fully operational and
                  available for use at the assigned orbital position of 101
                  degrees W. L. and meets certain other requirements specified
                  in the agreement between AvData and Satellite Operator)
                  during the second calendar quarter of 1999. Satellite
                  Operator has applied to the FCC for authorization to locate
                  GE-4 at 101 degrees W. L. for the purpose of replacing SN-4.

         (b)      The Satellite Operator has the right to modify the mission of
                  GE-4 (for example, to replace another existing in-orbit
                  satellite operated by the Satellite Operator due to a
                  satellite failure) the Satellite Operator has represented to
                  AvData that it would replace SN-4 with the next available
                  satellite (currently GE-6). The Satellite Operator has
                  represented to AvData that SN-4 has the fuel and capability
                  to remain in orbit until December 2004.

         (c)      Under AvData's agreement with Satellite Operator, the
                  Satellite Operator may, at its sole discretion, offer certain
                  capacity on SCPC Transponder(s) capable of supporting South
                  American downlink and uplink coverage. Such revised service
                  would be subject to mutually agreed upon pricing, allocated
                  power and Transponder performance specifications. If
                  Satellite Operator offers such capacity, AvData will notify
                  Customer of the terms and conditions on which AvData would
                  offer such capacity to Customer. Customer shall have thirty
                  (30) days thereafter to accept such offer. AvData shall be
                  under no obligation to make such capacity available on GE-4
                  or any other satellite.


            Second Amended and Restated Satellite Services Agreement
Page 10                AvData Systems, Inc - Proprietary



*  CONFIDENTIAL INFORMATION HAS BEEN DELETED. THE OMITTED MATERIAL HAS BEEN 
   FILED SEPARATELY WITH THE COMMISSION PURSUANT TO AN APPLICATION FOR 
   CONFIDENTIAL TREATMENT.

<PAGE>   11

                          SECOND AMENDED AND RESTATED
                   SATELLITE SERVICES SUPPLEMENTAL AGREEMENT


         (d)      Provided that this Agreement is still in effect on the date
                  GE-4 becomes "Commercially Operational", AvData shall provide
                  and Customer shall take, in lieu of [*] on SN-4, [*] SCUs on
                  GE-4 for the remainder of the Service term of this Agreement.
                  SCU service on GE-4 shall commence (and SCU service on SN-4
                  shall be discontinued) on the date AvData transitions its
                  capacity on SN-4 to GE-4 in accordance wit its agreement with
                  the Satellite Operator.

         (e)      Neither the Satellite Operator nor AvData shall have any
                  liability whatsoever in connection with the launch or
                  manufacture of GE-4, including but not limited to, GE-4
                  launch delay or failure, GE-4 is delayed in operation, or
                  GE-4 is positioned at an orbital location other than 101 W.
                  L.

         (f)      Until SN-4 is replaced by GE-4 (or other suitable satellite),
                  AvData will provide to PageMart up to [*] of Satellite
                  Capacity on G-3R with Hub services at [*]. Such capacity will
                  be used to support PageMart VNI offshore sites (located in the
                  Caribbean area, Hawaii and Alaska). Successful replacement of
                  SN-4 with a satellite capable of supporting such offshore
                  sites will relieve AvData of all responsibility regarding this
                  temporary commitment.

         (g)      If a Satellite Capacity Failure occurs with respect to
                  Satellite Capacity provided by AvData on G-3R prior to SN-4
                  being replaced by GE-4 (or other suitable satellite), AvData
                  will provide to PageMart up to [*] of Satellite Capacity on
                  an alternative satellite with Hub services [*]. Such capacity
                  will be used to support PageMart VNI offshore sites (located
                  in the Caribbean area, Hawaii and Alaska). Successful
                  replacement of SN-4 with a satellite capable of supporting
                  such offshore sites will relieve AvData of all responsibility
                  regarding this commitment.


            Second Amended and Restated Satellite Services Agreement
Page 11                AvData Systems, Inc - Proprietary




*  CONFIDENTIAL INFORMATION HAS BEEN DELETED. THE OMITTED MATERIAL HAS BEEN 
   FILED SEPARATELY WITH THE COMMISSION PURSUANT TO AN APPLICATION FOR 
   CONFIDENTIAL TREATMENT.