<PAGE>

                                                                   EXHIBIT 10.52

   Confidential Materials omitted and filed with the Securities and Exchange
   Commission.
                           Asterisks denote omissions.

                                 AMENDMENT No. 1
                                     to the
                                    AGREEMENT

Between,

     AG Communication Systems Corporation, a Delaware corporation, with offices
     located at 2500 West Utopia Road, Phoenix, Arizona 85027 (hereinafter
     referred to as "AGCS"),

And,

     Cellular Express, Inc., a Massachusetts corporation d/b/a Boston
     Communications Group, with offices located at 100 Sylvan Road, Woburn,
     Massachusetts 01801 (hereinafter referred to as "Company").


WHEREAS, AGCS and Company entered into an Agreement, dated November 16, 1998
(the "Agreement"), by the terms of which AGCS agreed to develop and port
Wireless Prepaid Services (WPS) solutions based on Company and/or industry
specifications, all as more fully set forth in the Agreement; and

NOW, THEREFORE, the parties agree as follows:


1.  The first paragraph of Article 14, Termination, shall be amended as follows:
                                       -----------

     This Agreement may not be terminated by the Company, at its sole
     discretion, prior to meeting all its payment obligations set forth in
     Attachment 1 of this Agreement.  Company may terminate this Agreement, at
     its sole discretion, at any time following completion of all its payment
     obligations set forth in Attachment 1 of this Agreement, on fifteen (15)
     days prior written notice to AGCS.  Upon termination by the Company,
     following its meeting all its payment obligations AGCS shall not have any
     further rights against the Company under this Agreement.  Should Company
     terminate this Agreement prior to meeting all its payment obligations, for
     any reason except default by AGCS, Company agrees to pay AGCS the amounts
     set forth in Attachment 1 of this Agreement.

2.   Section 26, Definitions, is hereby added to the Agreement:
                 -----------

            26.  Definitions.
                 -----------

          (a) "WPS Software" means the [**] Call Control and Protocol Software,
     UWC WPS Release 1.0, TIA WPS Release 1.0 and GSM WPS Release 1.0, which
     interfaces with Company's rating engine and Company's Intelligent
     Peripheral (IP) as detailed in the following Company documents: Company's
     WIN prepaid business requirements [**].

          (b) "UWC WPS Release 1.0" means a Wireless Intelligent Network (WIN)
     based UWC WPS solution based on UWC Prepaid Charging (PPC), Phase 1,
     service specifications with modifications/additions per Company functional
     specifications as defined in the first paragraph of Section 1, GENERAL, of
     Attachment 1.

          (c) "TIA WPS Release 1.0" means the mutually agreed to capabilities of
     UWC WPS Release 1.0 plus a TIA WPS solution based on TIA TR-45.2.2.4 WIN,
     Phase 2 (Package A) specifications with modifications/additions per Company
     functional specifications as defined in the first paragraph of Section 1,
     GENERAL, of Attachment 1.

          (d) "GSM WPS Release 1.0" means a GSM CAMEL based WPS solution in
     accordance with mutually agreed to functional specifications.

                                       1
<PAGE>

     Confidential Materials omitted and filed with the Securities and Exchange
     Commission.
                          Asterisks denote omissions.


3.   The first paragraph of Section 1, GENERAL, of Attachment 1 shall be amended
     as follows:

     AG Communication Systems (AGCS) will develop and port the following
     Wireless Prepaid Services (WPS) solutions for Boston Communications Group
     (BCGI): a Roaming WPS solution based on BCGI's submitted technical
     specification [**] and BCGI's roaming functional specifications to be
     provided by BCGI; a Wireless Intelligent Network (WIN) based UWC WPS
     solution based on UWC Prepaid Charging (PPC), Phase 1, service
     specifications with modifications/additions per BCGI functional
     specifications and, a TIA WPS solution based on TIA TR-45.2.2.4 WIN, Phase
     2 (Package A) specifications with modifications/additions per BCGI
     functional specifications, which is expected to be standardized sometime in
     1999. Additionally, BCGI may request, and AGCS agrees, to develop GSM CAMEL
     WPS as defined in the following paragraph.

4.   The second paragraph of Section 1, GENERAL, of Attachment 1 shall be
     amended as follows:

     AGCS will develop a WIN based UWC WPS solution for delivery by April 1,
     2000. This solution will interface with BCGI's rating engine and BCGI's IP
     as detailed in the following BCGI documents: BCGI's WIN prepaid business
     requirements [**]; and a WIN prepaid functional specification to be
     provided by BCGI. AGCS will migrate this solution to a TIA WIN Phase 2
     solution within nine months of when this standard becomes available. If
     BCGI requests AGCS to develop GSM CAMEL WPS, , AGCS will develop WIN based
     UWC/TIA WPS solution only on the [**] platform and will develop GSM CAMEL
     WPS on the [**] platform. BCGI must notify AGCS in writing prior to January
     1, 2000, if they wish to have AGCS develop GSM CAMEL WPS on the [**]
     platform or to develop WIN based UWC/TIA WPS on a second platform, either
     the [**] platform. If written notification is not received by AGCS prior to
     January 1, 2000, AGCS shall develop GSM CAMEL WPS on the [**] platform in
     lieu of development of WIN based UWC/TIA WPS on a second platform. AGCS
     shall deliver the selected solution (UWC/TIA WPS solution developed to run
     on a second platform or GSM CAMEL WPS) nine months after written request by
     BCGI to develop such solution or September 1, 2000, whichever is earlier.

     The price for the UWC/TIA/GSM WPS solutions referred to above shall be [**]
     to be invoiced in accordance with the schedule set forth in Payment Terms.

5.   The third paragraph of Section 1, GENERAL, of Attachment 1 shall be amended
     as follows:

     AGCS will develop and port the roaming solution to BCGI specifications for
     [**].  This price includes BCGI exclusive license of the roaming solution.
     Maintenance for this is included throughout December 31, 2001.

6.   The fourth paragraph of Section 1, GENERAL, of Attachment 1 shall be
     deleted in its entirety.

7.   The fifth paragraph of Section 1, GENERAL, of Attachment 1 shall be amended
     as follows:

     Annual maintenance fees, in accordance with the level of support provided
     by AGCS, for service bureau usage of UWC/TIA WPS and GSM CAMEL WPS will be
     as follows:

<TABLE>
<CAPTION>

--------------------------------------------------------------------------------------------------
                                                 FIRST LEVEL SUPPORT       SECOND LEVEL SUPPORT
--------------------------------------------------------------------------------------------------
<S>                                                  <C>                       <C>
First Platform* with one Application                     [**]                      [**]
--------------------------------------------------------------------------------------------------
2nd Platform with one Application                        [**]                      [**]
--------------------------------------------------------------------------------------------------
Each Successive Platform w/one Application               [**]                      [**]
--------------------------------------------------------------------------------------------------
Two Applications on the same platform add:               [**]                      [**]
--------------------------------------------------------------------------------------------------
</TABLE>

                                       2
<PAGE>

   Confidential Materials omitted and filed with the Securities and Exchange
   Commission.
                          Asterisks denote omissions.

     *  Platform consists of the following scenarios:

     1.   One system with live customers and one hot standby system.
     2.   A mated pair each running at no more that 50% capacity utilization.
     3.   A mated pair each running at no more that 50% capacity utilization
          each with a hot standby.

     The fee for the maintenance to be provided to BCGI by AGCS shall be
     invoiced quarterly by AGCS beginning thirty (30) days prior to the
     expiration of the existing warranty or maintenance period, payable thirty
     (30) days from invoice date.  First level of support will validate the
     problem reported and isolate the problem to the WPS Software.  Non revenue
     generating installations, including lab and back-up units, will not be
     subject to maintenance fees.

8.   The seventh paragraph of Section 1, GENERAL, of Attachment 1 shall be
     amended as follows:

     The Agreement does not preclude BCGI from developing Intelligent Network
     (IN) Service Logic for prepaid or any other IN applications.

9.   The eight paragraph of Section 1, GENERAL, of Attachment 1 shall be amended
     as follows:

     BCGI will have an unlimited, fully paid and perpetual license (excluding
     source code and maintenance) to the UWC/TIA and/or GSM CAMEL, if BCGI
     requests AGCS to develop GSM CAMEL WPS.  AGCS will develop UWC/TIA WPS
     solution on the [**] initially to be delivered by April 1, 2000.  If BCGI
     chooses UWC/TIA WPS solution to be developed to run on a second platform,
     one of the following platforms may be used: [**].  Should BCGI choose to
     have AGCS develop GSM CAMEL WPS, the GSM CAMEL WPS solution shall be
     developed to run on the [**] platform.

     If BCGI chooses development of any of the applications on the [**]
     platform, BCGI and AGCS will evenly share the cost of this platform for the
     purpose of development and testing.  Prior to September 1, 2003, BCGI may
     elect to reimburse AGCS for the cost paid by AGCS for the above platform
     jointly purchased for development and testing, if, BCGI wishes to take
     ownership of this platform.

     AGCS agrees to place the source code in escrow within 30 days following
     acceptance of the software by BCGI, upon mutually agreed terms which shall
     include the provision that the source code shall be released to BCGI in the
     event that AGCS or its successor ceases operations or is otherwise unable
     or refuses in writing to maintain the software.

10.  Payment Terms in Section 1, GENERAL, of Attachment 1 shall be amended as
     follows:

<TABLE>
<CAPTION>
Payment Terms:
     ROAMING SOLUTION
     Schedule                                 %    Amount    Responsibility   Date
     ----------------------------------------------------------------------------------
<S>                                        <C>    <C>      <C>             <C>
     Contract Signature                       25%  [**]
     Functional Specifications (Roaming)       0%  [**]      BCGI             December 7, 1998
     Final Design Specifications (Roaming)    15%  [**]      AGCS/BCGI        January 18,1999
     Integration Testing (Roaming)            10%  [**]      AGCS             Starts June 1999
     Final Acceptance(Roaming)                10%  [**]      BCGI             Ends July 1999
     Commercial Use (Roaming)                 25%  [**]      BCGI             August 1999
     Integration testing: SCP-Rating
     for 1 platform (UWC/TIA WPS solution)    15%  [**]              (on delivery)
                                             ----------
     TOTAL                                   100%  [**]

</TABLE>


                                   3
<PAGE>

   Confidential Materials omitted and filed with the Securities and Exchange
   Commission.
                          Asterisks denote omissions.
<TABLE>
<CAPTION>

                 UWC/TIA/GSM WPS Solution for Service Bureau*
<S>            <C>             <C>
     Amount    Responsibility  Invoice Date
     ------------------------------------------------------------
     [**]      BCGI            At Signature
     [**]      BCGI            Acceptance of 1st Platform
     [**]      BCGI            Upon delivery of the 2nd Platform
     [**]      BCGI            January 1, 2001
     [**]      BCGI            May 1, 2001
</TABLE>

     *These payments cover use of the applications in a service bureau
     environment running on one or more BCGI or carrier owned SCPs connected to
     BCGI's service bureau rating and database engine.

     System Sales shall be governed by the terms and conditions set forth in
     Attachment 3 to this Amendment No. 1.  Maintenance for System Sales shall
     be governed by the terms and conditions set forth in Attachment 4 to this
     Amendment No. 1.

11.  Advance Payments in Section 1, GENERAL, of Attachment 1 shall be deleted in
     its entirety.

12.  The first paragraph of Section 3, UWC/TIA WPS SOLUTION, of Attachment 1
     shall be deleted in its entirety.

13.  The second paragraph of Section 3, UWC/TIA WPS SOLUTION, of Attachment 1
     shall be deleted in its entirety.

14.  Article 21, Audit, of the Agreement shall be deleted in its entirety.
                 -----

15.  Article 23, Maintenance, of the Agreement shall be amended as follows:
                 -----------

     23.  Maintenance BCGI has the option to purchase maintenance, as set forth
          in Attachment 4 to this Amendment No. 1, for an initial term of twelve
          (12) months following the end of the warranty period provided by AGCS
          for the WPS Software. AGCS' TAC support will be provided and that
          maintenance will correct errors or deficiencies in the operation and
          functioning of the application as required by the specifications.
          Maintenance does not include additional or enhanced functionality or
          additional or enhanced features to the software, except that provided
          for in Attachment 1.

16.  Article 20, Acceptance, of the Agreement shall be amended as follows:
                 ----------

          The first sentence of 20.1 should be amended as follows, the remainder
          of the article remains the same:

               Prior to delivery of the commercial Roaming WPS Software solution
               and any WPS Software solution to Company, AGCS shall perform the
               internal testing that is appropriate to provide reasonable
               assurance that each software solution will perform in conformance
               with their specifications.

17.  Article 20, Acceptance, of the Agreement shall be amended by adding a
                 ----------
Section 20.6 as follows:

     20.6 If BCGI chooses GSM CAMEL WPS Software, and if the GSM CAMEL WPS
          Software solution fails to perform in conformance with its
          specifications during the acceptance test period, AGCS shall extend
          the acceptance test period, as mutually agreed by the parties, and
          shall correct material deficiencies. If AGCS is unable to correct
          material deficiencies by the date agreed to by both parties, Company
          shall be refunded the amount paid for the GSM CAMEL WPS Software
          solution.

                                       4
<PAGE>

18.  Unless otherwise modified or amended by this Amendment No. 1, the Agreement
     remains in full force and effect.


IN WITNESS WHEREOF the parties have signed this Amendment No. 1 in two originals
as of the date or dates below written.


Cellular Express, Inc.                      AG Communication Systems Corporation


By:  /s/ Kevin Thigpen                         By:  /s/ Charles Schulz
     -----------------------------------          ------------------------------


Name:  Kevin Thigpen                           Name:  Charles Schulz
     -----------------------------------            ----------------------------


Title: Vice President & General Manager        Title:  VP/GM PAG
      ----------------------------------             ---------------------------


Date:  August 24, 1999                         Date:  August 26, 1999
     -----------------------------------            ----------------------------


                                       5
<PAGE>

   Confidential Materials omitted and filed with the Securities and Exchange
   Commission.
                          Asterisks denote omissions.


                                  Attachment 3
                                  ------------

                                  SYSTEM SALES

1.   SCOPE

1.1  The following terms and conditions shall apply to transactions in which AG
     Communication Systems Corporation (AGCS) furnishes WPS Software to Boston
     Communications Group (BCGI) as a distributor for purposes of (i)
     sublicensing WPS Software throughout the world and (ii) using WPS Software
     to provide installation, training and support services to BCGI customers
     worldwide.

1.2  Following June 1, 2002 the parties may negotiate a mutually acceptable
     agreement to replace the current terms and conditions.

2.   DEFINITIONS

     All initially capitalized terms that are not specifically defined in this
     Attachment 3 shall have the meanings ascribed to them in the Agreement.
     Additionally, the following terms and their definitions shall apply:

2.1  "Enhancement" means any upgrade or new feature not included in "WPS
     Software" as defined in Amendment No. 1 to the Agreement that increases
     capability of the WPS Software and any Documentation related to the
     Enhancement. Enhancements will be signified by either a new release number,
     (e.g., Release 4.0 succeeding Release 3.0) for the addition of major
     capabilities, or a software point release to identify the addition of a
     minor capability to the software (i.e., Release 4.1, the number 1
     indicating a software point release to Release 4.0 of the software).
     Enhancements will be made available to LICENSEE at a mutually agreed upon
     price and licensed pursuant to this Agreement or to an amendment to this
     Agreement, or a separate agreement or written order between the parties.

2.2  "Licensed Materials" means the WPS Software (as defined below in Section
     26(a) of the Agreement) and Related Documentation; no source code versions
     of computer programs are included in Licensed Materials.

2.3  "Modification" means a revision or minor change to the WPS Software
     intended to correct errors or nonconformance with the Related
     Documentation. Modifications do not include Enhancements. An issue number
     to the release itself (e.g., release 2.0 Issue 1) will signify
     modifications. Modifications are provided at no charge to BCGI under
     warranty coverage and the Software Maintenance Agreement.

2.4  "Related Documentation" means the printed materials provided with the WPS
     Software describing the WPS Software and their installation and use.

2.5  "Service Providers" means entities that are sublicensed, directly or
     indirectly, by BCGI to use the WPS Software and to provide Wireless Prepaid
     services to their respective subscribers. Service Providers may not
     sublicense the WPS Software, but may permanently assign or transfer their
     license to use the WPS Software to a third party, provided such party is
     not a competitor of AGCS and agrees to be bound in writing to the terms and
     conditions of the sublicense.

2.6  "Third Party Vendor(s)" means any and all third party hardware and/or
     software vendor(s) whose hardware and/or software are required for the
     operation of the WPS Software.

3.   LICENSE GRANT


3.1  AGCS grants BCGI, subject to the fees set forth in Section 8, a [**] right
     to sublicense, market and distribute copies of the Licensed Materials in
     object code form. AGCS shall also provide BCGI with one

                                       1
<PAGE>

    Confidential Materials omitted and filed with the Securities and Exchange
    Commission.
                          Asterisks denote omissions.


(1) demonstration copy of the Licensed Materials solely for the purpose of
marketing and promoting the WPS Software.

(a)  BCGI may directly, or indirectly through distributors, grant perpetual
     sublicenses of the Licensed Materials in object code format to Service
     Providers for such Service Provider's own internal use, subject to payment
     by BCGI of the fees set forth in Section 8. BCGI shall cause the Service
     Providers to execute a sublicense agreement containing the minimum terms
     and conditions set forth in this Agreement. AGCS acknowledges that the
     terms and conditions of the sublicense agreement are subject to
     negotiations with the Service Providers, but that the final agreement will
     contain substantially similar terms. No sublicense shall release BCGI from
     its obligations under this Agreement.

(b)  BCGI may install the WPS Software on approved hardware and operating
     system, along with other BCGI or third party software applications. Should
     the hardware vendor modify the operating system, AGCS shall make normal
     customary changes to its WPS Software, based upon its multiple platform
     provider experience, provided the changes address validated customer
     opportunities. This effort shall only require recompiling and regression
     testing. Beyond the parameters set forth in this Section 3.1(b), AGCS
     agrees to make necessary changes or additions, including redesign of the
     WPS Software, in accordance with terms to be agreed to between the parties.

(c)  AGCS hereby grants BCGI a license to translate, copy and paraphrase, the
     Related Documentation, as necessary to fulfill the requirements of Service
     Providers and to provide an integrated prepaid services product. AGCS shall
     not be liable for any loss or damage caused directly or indirectly by
     faulty translations.


3.2  The WPS Software shall be licensed on a per subscriber basis as outlined in
     Section 8.1 of this Attachment 3.

3.3  The WPS Software will be marketed and distributed by BCGI under the AGCS
     [**] trademark under the provisions of Section 11 of this Attachment 3.

4.   RELATIONSHIP OF THE PARTIES

4.1  The relationship of the parties under this Agreement shall be and at all
     times remain one of independent contractors.  All persons furnished by BCGI
     shall be considered solely BCGI's employees or agents, and BCGI shall be
     responsible for payment of all unemployment, social security and other
     payroll taxes including contributions from them when required by law.  All
     persons furnished by AGCS shall be considered solely AGCS' employees or
     agents, and AGCS shall be responsible for payment of all unemployment,
     social security and other payroll taxes including contributions from them
     when required by law.

5.   OBLIGATIONS

5.1  AGCS Obligations:

(a)  At its expense, provide one (1) suitcased sales training course open to all
     members of BCGI's sales team so that BCGI will be able to effectively
     market and sublicense the Licensed Materials.  BCGI will provide for
     related lodging and transportation expense for AGCS instructors delivering
     the suitcased courses.  Additional courses will be provided at AGCS' then
     current prices.
                                       2
<PAGE>

   Confidential Materials omitted and filed with the Securities and Exchange
   Commission.
                          Asterisks denote omissions.

(b)  At BCGI's expense, provide technical assistance for sales visits, when such
     is requested by BCGI (including travel and other time not spent directly
     with the Service Provider).

(c)  AGCS shall provide all Related Documentation to BCGI in English.  BCGI
     shall have a right to translate the documentation provided by AGCS.  AGCS
     shall not be liable for any loss or damage caused directly or indirectly by
     faulty translations.

(d)  Provide second level support to BCGI for the WPS Software sublicensed to
     Service Providers.  This includes twenty-four (24) hours of daily support,
     seven (7) days per week and includes technical support able to resolve
     problems that arise from a Service Provider with the application during the
     extended warranty period if purchased separately.  Out-of-warranty services
     are available as provided in Attachment 4.

(e)  Upon request by BCGI, assign project management personnel to work with BCGI
     on Service Provider projects at a rate of [**] per hour or upon a mutually
     agreed to fixed project price.

(f)  If requested by BCGI for foreign business opportunities, AGCS may modify
     the AGCS Software to qualify for homologation, comply with local protocols
     and standards and to achieve other types of local certification and product
     requirements mandated by foreign governments.  In countries where AGCS has
     already "localized" the WPS Software, AGCS agrees to provide such versions
     to BCGI at no additional charge.   If BCGI requests AGCS to modify the WPS
     Software to achieve localization for an identified business opportunity,
     the parties shall mutually agree to the fees and terms for such
     localization.

5.2  BCGI Obligations

(a)  Market the Licensed Materials as AGCS products and not as a product of
     BCGI.  However, nothing in this Agreement will require BCGI to market or
     sublicense any Licensed Materials.

(b)  Provide training for Service Providers as BCGI deems appropriate.

(c)  Provide first level support for the WPS Software.  This level of support
     will validate the problem reported and isolate the problem to the WPS
     Software whereby BCGI will report to AGCS for corrective action.

(d)  Provide all Third Party Vendor software and hardware.

(e)  Provide all integration and installation services for the WPS Software.

6.   ORDERS

6.1  Any written order submitted by BCGI shall contain information necessary for
     furnishing WPS Software including, without limitation, the date of the
     order, any applicable product identifier, Service Provider name and
     delivery location, requested date of shipment and extended warranty
     information. All orders submitted by BCGI and order acknowledgements
     submitted by AGCS shall be deemed to incorporate and are subject to the
     terms and conditions of this Agreement as well as any supplemental terms
     and conditions mutually agreed by both AGCS and BCGI in writing. Unless
     both parties expressly agree upon all supplemental terms and conditions in
     writing, such supplemental terms and conditions shall be null and void.

6.2  No written order shall be binding on AGCS unless and until accepted in
     writing by AGCS, which may accept or request a clarification of any order;
     provided, however, that if AGCS fails to respond to BCGI in writing
     (acceptance or rejection) within ten (10) business days from receipt of the
     order, AGCS shall be deemed to have accepted the order.
                                       3
<PAGE>

   Confidential Materials omitted and filed with the Securities and Exchange
   Commission.
                          Asterisks denote omissions.

6.3  In no event shall the preprinted terms and conditions of any written order
     or acknowledgment or other similar form alter or amend any provision of
     this Agreement even if signed by either or both parties. An inadvertent
     omission of reference to this Agreement in a written order or
     acknowledgment shall not affect the application of this Agreement to such
     written order or acknowledgment.

6.4  All packing, documentation and arrangements for international shipments
     shall be the responsibility of BCGI. AGCS shall only arrange shipment of
     the WPS Software to destinations within the United States, and in the
     absence of written instructions from BCGI, shall ship the WPS Software in a
     manner consistent with AGCS' usual shipping practices, F.O.B. shipping
     point. Risk of loss for the deliverable shall pass to BCGI upon delivery to
     the carrier. Transportation and shipping charges, including, without
     limitation, any costs incurred by AGCS relating to packing, storage,
     documentation and similar items which result from special shipping
     instruction of BCGI, and the cost of any insurance which BCGI may request
     in connection with the WPS Software, shall be added to the price stated on
     the invoice and shall be paid by BCGI at the time that payment of the
     purchase and/or license price for the WPS Software is due and payable.

6.5  BCGI shall have the obligation of obtaining all required export licenses
     for the WPS Software where the WPS Software will be exported from the
     United States.

6.6  In the event an order requires custom modifications or equipment, BCGI may,
     in writing, request that AGCS reschedule the order under this Agreement in
     whole or in part (i.e., request a new delivery date for the WPS Software
     ordered), cancel, or reconfigure any order within sixty (60) days of
     scheduled ship date. In this event, BCGI shall be subject to the following
     charges:

<TABLE>
<CAPTION>

No. Days Request is        Cancellation   Reconfiguration/
Received Prior to Ship     Charges        Rescheduling
<S>                       <C>           <C>

Within 31 - 60             [**]           [**]
Within 16 - 30             [**]           [**]
Within  1 - 15             [**]           [**]

</TABLE>

6.7  In the event an order does not require custom modifications or equipment,
     BCGI may, in writing, request that AGCS reschedule the order under this
     Agreement in whole or in part (i.e., request a new delivery date for the
     WPS Software ordered), cancel, or reconfigure any order within sixty (60)
     days of scheduled ship date. In this event, BCGI shall be subject to the
     following charges:

<TABLE>
<CAPTION>

No. Days Request is        Cancellation   Reconfiguration/
Received Prior to Ship     Charges        Rescheduling
<S>                      <C>           <C>

Within 31 - 60             [**]           [**]
Within 16 - 30             [**]           [**]
Within  1 - 15             [**]           [**]
</TABLE>

7.   ACCEPTANCE

7.1  The WPS Software shall be deemed accepted upon shipment by AGCS to BCGI for
     systems sales provided acceptance testing, as defined in Section 20 of the
     Agreement, by BCGI, of the same WPS Software for service bureau usage has
     been completed. If acceptance testing by BCGI as defined in Section 20 of
     the Agreement for the same WPS Software for service bureau usage or an
     enhanced version of the WPS Software has not been completed, the WPS
     Software shall be deemed accepted following acceptance testing by BCGI as
     defined in Section 20 of the Agreement for the initial shipment only of the
     WPS Software for system sales.
                                       4
<PAGE>

   Confidential Materials omitted and filed with the Securities and Exchange
   Commission.
                          Asterisks denote omissions.

8.   FEES

8.1  BCGI hereby agrees to pay AGCS [**] per subscriber for system sales up to a
     total payment of [**] and [**] per subscriber for such sales after the
     total of such payments exceeds [**]. BCGI shall be responsible for ordering
     a license in minimum subscriber blocks of [**]. The fee for a system sale
     shall be determined at the time of sale based upon the number of
     subscribers that the system which is sold is intended to serve, as stated
     prior to the sale in writing to BCGI by the customer to whom the system is
     sold. In the event a Service Provider orders a system expansion from BCGI,
     BCGI will pay AGCS the applicable per subscriber fee determined at the time
     of the expansion based upon the number of subscribers that the system
     expansion which is sold is intended to serve, as state prior to the sale in
     writing to BCGI by the Service Provider to whom the system is sold.

8.2  AGCS shall invoice BCGI upon shipment and/or acceptance, in accordance with
     Section 7.1 of this Attachment 3, of the WPS Software. All invoices shall
     be issued in accordance with the billing terms set forth in Section 22,
     Billing Terms, of the Agreement. AGCS' invoices shall contain (i) BCGI's
     --------------
     "invoice to" and "ship to" addresses as specified by the Order, (ii) Order
     number, (iii) applicable fee, and (iv) reference to this Agreement.

8.3  All prices are F.O.B. shipping point.

8.4  All amounts expressed herein are in U.S. dollars.

8.5  All prices for WPS Software are exclusive of all federal, state, provincial
     and local excise, sales, use, value-added, occupational, levies,
     assessments, import duties and like taxes which may be imposed by the
     United States of America, or by any political subdivision of the United
     States, or by any country or political subdivision in connection with any
     transaction contemplated by this Agreement and/or WPS Software licensed by
     BCGI hereunder, excluding taxes based upon AGCS' possession thereof prior
     to originally scheduled delivery and taxes on AGCS' net income from the
     transaction. Payment of all such taxes shall be assumed and paid for by
     BCGI. BCGI shall be responsible for providing, in a timely manner, all
     documentation in the nature of exemption certificates or otherwise,
     necessary to allow AGCS to refrain from collections, such as sales tax,
     which it would otherwise be obligated to make. BCGI agrees to indemnify and
     hold AGCS harmless for all taxes and this obligation shall survive any
     termination of this Agreement.

9.   Audit

9.1  Not more than twice a year AGCS may audit, or designate an independent
     certified auditor to audit the directly relevant records of BCGI during
     BCGI's regular business hours to determine whether the amount paid to AGCS
     by BCGI is accurate. Any expenses of such audit shall be born by AGCS,
     unless the audit determines that the amount paid to AGCS by BCGI is
     inaccurate by more than ten (10%) percent, in which case all reasonable
     expenses of the audit will be born by BCGI. BCGI will be required to pay
     AGCS any amount owed. In the event that the audit determines that BCGI has
     made an overpayment, AGCS shall pay the amount of such overpayment to BCGI.

9.2  The number of subscribers is limited to the license(s) acquired by a
     Service Provider. In the event the customer orders a system expansion from
     BCGI, BCGI shall be responsible for providing AGCS a written order for a
     license(s), in minimum subscriber blocks of [**], at fees set forth in
     Section 8.1, to accommodate the number of subscribers in excess of the
     authorized quantity. AGCS will invoice BCGI for applicable license at the
     fees set forth in Section 8.1 and BCGI agrees to pay AGCS the applicable
     license fee upon receipt of said invoice.

9.3  Any relevant documents shall be conclusively presumed as accurate after six
     (6) months from date of delivery to AGCS by BCGI and shall be excluded from
     auditing.
                                       5
<PAGE>

9.4  Any information derived from BCGI's reports or records shall be maintained
     in confidence by AGCS as confidential information of BCGI pursuant to
     Section 4 of the Agreement.

10.  TITLE

10.1 This Agreement is not intended to and shall not be construed to convey or
     otherwise transfer title to, ownership of, or any proprietary rights in,
     the Licensed Materials to BCGI or BCGI's Service Providers.

11.  INFRINGEMENT OF PATENTS, TRADEMARKS AND COPYRIGHTS

11.1 In the event of any claim, action, proceeding or suit by a third party
     against BCGI alleging an infringement of any patent, copyright, trademark
     or trade secret by reason of the possession, use, license or distribution,
     in accordance with AGCS' specifications, of any Licensed Materials
     furnished to BCGI under this Agreement, AGCS at its expense, will defend
     and hold harmless BCGI and its Service Providers in any such proceeding
     subject to the conditions and exceptions stated below. AGCS will reimburse
     BCGI and its Service Providers for any cost, expense or attorney's fee,
     incurred at AGCS' written request or authorization, and will indemnify and
     hold harmless BCGI and its Service Providers against any liability assessed
     against BCGI on account of such infringement.

11.2 In addition, if BCGI's possession, use, license or distribution rights are
     likely to be or shall be enjoined, AGCS will, at its expense and at its
     option, either: (1) replace the enjoined Licensed Material furnished
     pursuant to this Agreement with a suitable substitute free of any
     infringement; or (2) modify it so that it will be free of the infringement
     without adversely affecting its functionality; or (3) procure for BCGI and
     the Service Providers a license or other right to use it; or (4) procure
     for BCGI a right to license it on terms no less favorable then the terms of
     this Agreement. If none of the foregoing options is available, AGCS will
     remove the enjoined Licensed Materials and refund to BCGI any amounts paid
     by BCGI.

11.3 BCGI shall give AGCS prompt written notice of all such claims, actions,
     proceedings or suits alleging infringement or violation and BCGI shall have
     the right, at its cost and expense, to cooperate in the defense of such
     action (including appeals or settlements). BCGI shall, upon AGCS' request
     and expense, furnish information and reasonable assistance to facilitate
     the defense and/or settlement of any such claim, action, proceeding, or
     suit. AGCS shall have no liability to BCGI whatsoever for any loss or
     damage resulting from a claim of infringement or wrongful use or a
     Proprietary Right based upon and arising from any unauthorized alteration
     or modification of the WPS Software or the use of the WPS Software in
     combination with hardware or software not furnished or recommended by AGCS
     or any WPS Software development based on a functional specification
     provided to AGCS by BCGI or a BCGI directed implementation of a functional
     specification provided to AGCS by BCGI (AGCS shall be liable under this
     paragraph should infringement be caused by a non BCGI directed
     implementation of a BCGI functional specification).

12.  WARRANTY, EXTENDED WARRANTY AND TECHNICAL ASSISTANCE

12.1 AGCS will warrant the first sublicense of each of the first releases of the
     Licensed Materials for a period of six (6) months from acceptance, all
     subsequent sublicenses of such Licensed Materials, as well as any
     enhancements thereof, will be warranted for a period of ninety (90) days
     from acceptance. AGCS will correct, at AGCS' expense, deficiencies in the
     WPS Software that are brought to AGCS' attention within the warranty
     period. Provided payment for extended warranty as set forth in Section 7.1
     of the Maintenance Agreement has been received by AGCS, extended warranty
     coverage takes effect on the date of expiration of the warranty provided by
     AGCS to BCGI. Extended Warranty includes AGCS Customer Support Center (CSC)
     support twenty-four (24) hours a day, seven (7) days a week.

13.  TRADEMARKS AND OTHER INDICIA

13.1 Licensed Materials licensed hereunder and the packaging therefor may bear
     certain trade names, trademarks, trade devices, logos, codes or other
     symbols of AGCS (herein "Indicia").  AGCS hereby grants

                                       6
<PAGE>

     BCGI permission to use Indicia in BCGI's marketing and advertising of, and
     in BCGI's publicity relating to, the Licensed Materials, PROVIDED such use
     conforms to AGCS standards and guidelines relating thereto which AGCS may
     furnish from time to time. AGCS may not use any of BCGI's trade names,
     trademarks, trade devices, logos, codes or other symbols in a manner that
     is likely to confuse the public concerning the relationship of the parties.
     Upon termination of this Agreement, BCGI shall immediately cease using
     AGCS' trademarks.

14.  MARKETING

14.1 BCGI shall have complete authority to market any or all of the Licensed
     Materials as it sees fit so long as BCGI meets the payment obligations set
     forth in this Agreement and does not otherwise violate AGCS' rights in the
     Licensed Materials. Nothing in this Agreement shall be construed to
     obligate BCGI to in any way market, distribute, ship or otherwise utilize
     any Licensed Materials or any portion thereof. It is understood that AGCS
     will only support one (1) major release behind the current commercial
     release.
                                       7
<PAGE>

15.  SURVIVAL OF OBLIGATIONS

15.1 The respective obligations of AGCS and BCGI under this Agreement which by
     their nature would continue beyond the termination, cancellation or
     expiration hereof, including without limitation, infringement and
     indemnification obligations, shall survive termination, cancellation or
     expiration hereof. All licenses and sublicenses purchased under this
     Agreement or an order shall survive termination, cancellation or expiration
     of this Agreement.

16.  LIMITATION OF LIABILITY

16.1 In no event shall either party be responsible for any incidental, special
     or consequential damages arising out of or in connection with this
     Agreement.

17.  EXPORT CONTROLS

17.1 In regard to the WPS Software as defined in this Agreement, BCGI will not
     transmit, release, export or reexport, directly or indirectly, in whole or
     in part, any proprietary information, technology, software or the source
     code for the software or direct product of such proprietary information,
     technology, or software: (i) to any country listed from time to time in the
     Country Groups D:1 and E:2 set forth in the United States Export
     Administration's list of Country Groups without a license exception or a
     license from the U.S. Department of Commerce; or, (ii) in contravention of
     the laws of the United States of America or the laws of any other country.
     The countries currently listed in the Country Groups D:1 and E:2 are:
     Afghanistan, Albania, Armenia, Azerbaijan, Belarus, Bulgaria, Cambodia,
     Cuba, Estonia, Georgia, Iran, Iraq, Kazakhstan, Kyrgyzstan, Laos, Latvia,
     Libya, Lithuania, Moldova, Mongolia, The People's Republic of China, North
     Korea, Romania, Russia, Sudan, Syria, Tajikistan, Turkmenistan, Ukraine,
     Uzbekistan and Vietnam. This clause shall survive any termination, release
     or time period set forth in this agreement.
                                       8
<PAGE>

                                  Attachment 4
                                  ------------

                         SOFTWARE MAINTENANCE AGREEMENT

This Software Maintenance Agreement ("Maintenance Agreement"), entered into this
26th day of August, ("Effective Date"), by and between AG COMMUNICATION SYSTEMS
CORPORATION, a Delaware corporation, with offices located 2500 West Utopia Road,
Phoenix, Arizona 85027 (hereinafter "AGCS") and CELLULAR EXPRESS, INC., a
Massachusetts corporation d/b/a Boston Communications Group, with offices
located at 100 Sylvan Road, Woburn, Massachusetts 01801 (hereinafter referred to
as "BCGI").


WHEREAS, AGCS and BCGI have entered into an Agreement (the "Agreement") by the
terms of which AGCS agreed to develop and port Wireless Prepaid Service (WPS
Software) solutions based on BCGI and/or industry specifications, all as more
fully set forth in the Agreement; and

WHEREAS, BCGI has requested AGCS to provide second line software maintenance and
support for the WPS Software in support of BCGI; and

WHEREAS, AGCS is willing to provide, and BCGI is willing to acquire maintenance
service for the WPS Software subject to the terms and conditions hereof;

NOW THEREFORE, the parties hereto agree as follows:

1.   SCOPE

1.1  The terms and conditions in this Maintenance Agreement are applicable to
     the following scenarios:

     a. BCGI sells systems containing WPS Software to Service Providers

     b. BCGI operates the WPS Software in a service bureau environment

     c.  BCGI operates service bureau environment for rating and database and
     links to a carrier installed Service Control Point (SCP) for WPS Software.

2.  DEFINITIONS

2.1 All initially capitalized terms that are not specifically defined in this
    Maintenance Agreement shall have the meanings ascribed to them in the
    Agreement.

3.   AGCS CUSTOMER SUPPORT CENTER

3.1 AGCS' Customer Support Center support shall be available to BCGI twenty-four
    (24) hours a day, seven (7) days a week by calling 1-888-888-2427. The
    service to be provided will be the following:

     3.1.1 Distribution of a master AGCS escalation chart matrix and ongoing
          updates. This matrix will include names, titles, and telephone numbers
          of individuals within the Customer Support Center organization for
          problem response escalation. AGCS agrees to respond to BCGI as stated
          in Article 2.3 below on a twenty four (24) hour a day basis in the
          event of an out of service condition. This support may be provided by
          AGCS' installation, or other qualified personnel.

     3.1.2 Telephone assistance in the diagnosis and resolution of WPS Software
          problems and assistance in expediting priority replacement software
          required on an emergency basis.

     3.1.3 On-line remote monitoring of sites, as mutually agreed, to provide
          assistance in problem identification and resolution. Such on-line
          monitoring may require a data connection agreement between the parties
          to regulate the method and extent of connection between the parties'
          computer
                                       1
<PAGE>

          networks. BCGI shall arrange in advance, such that Service Provider
          will have an appropriate access port available.

     3.1.4 Routine telephone assistance in the support of the initial
          implementation of newly developed software modifications to the WPS
          Software.

     3.1.5 Furnish software work arounds or updates for software that is not
          compliant with the Related Documentation.

3.2  When BCGI refers trouble to the AGCS Customer Support Center, the caller
     must be given a case number and a mutually agreed upon priority level if
     resolution cannot be completed over the telephone. The table provided below
     describes the four levels of priority used by the Customer Support Center.
     The Customer Support Center shall provide the caller a verbal status,
     disposition or resolution of the reported problem within two (2) hours of
     notification for priority levels one and two. At the discretion of BCGI,
     the problem may be escalated in accordance with the following escalation
     matrix:


<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------
  PRIORITY     URGENCY                                     DESCRIPTION
========================================================================================================
<S>          <C>
   1           Critical  The Service Provider's network is down and inoperable.  All work has stopped
                         and the situation is causing a critical impact to the Service Provider's
                         business operations and productivity. No workaround is available.
--------------------------------------------------------------------------------------------------------
   2           High      The Service Provider's network is severely limited or degraded.  The situation
                         is causing a significant impact to certain portions of the Service Provider's
                         business and productivity.  No workaround is available.
--------------------------------------------------------------------------------------------------------
   3           Medium    The Service Provider's network is slightly limited or degraded.  The situation
                         has impaired network operations, but most business operations and user
                         productivity continue. A workaround or alternate configuration is available.
--------------------------------------------------------------------------------------------------------
   4           Low       The Service Provider's network or user productivity are not affected.  Service
                         Provider calls in with informational inquiries, documentation issues, upgrade
                         requests, requests for a new feature or function or requires additional
                         information.
--------------------------------------------------------------------------------------------------------
</TABLE>

3.3  The Customer Support Center shall respond to all emergency calls within two
     (2) hours.

3.4  AGCS shall cooperate in providing guidelines to ensure the necessary
     tracking and resolution of service complaints.

3.5  In order to perform diagnostic testing and fault isolation with minimal
     system interruption, AGCS reserves the right to obtain remote access to the
     application running at the site reporting the problem. If remote access is
     requested by AGCS for maintenance purposes, and access is denied or
     otherwise not available to AGCS, the response times and time intervals for
     resolution will be expanded to adjust for the time access is not available.

3.6  If the parties agree that AGCS will provide first-call support, BCGI shall
     provide AGCS with the name, address and telephone number of a designated
     system administrator and alternate for the site(s) at which the WPS
     Software is installed. BCGI shall also provide AGCS with all information,
     documentation, technical assistance and access to the WPS Software as AGCS
     may reasonably require to perform pursuant to this Maintenance Agreement.
     The system administrator and alternate shall have a working knowledge of
     the WPS Software. Only the system administrator and alternate are
     authorized to contact AGCS for maintenance service. BCGI shall immediately
     notify AGCS of any changes with respect to the name, address or telephone
     number of the system administrator and alternate. BCGI shall be responsible
     for providing adequate system engineering and hardware capabilities for the
     WPS Software to function properly.
                                       2
<PAGE>

3.7  All corrective software and documentation provided by AGCS for the WPS
     Software under this Maintenance Agreement shall become and remain the
     exclusive property of AGCS and shall be licensed to BCGI under the license
     provisions of the Agreement.

3.8  AGCS' obligations hereunder are contingent upon BCGI's compliance with the
     terms of the Agreement and this Maintenance Agreement. AGCS reserves the
     right to reject for maintenance service any WPS Software which has not been
     on continuous maintenance service by AGCS, or has been repaired by BCGI or
     a third party other than at the direction of AGCS. BCGI shall be
     responsible for all charges to restore any WPS Software to a condition
     acceptable to AGCS for inclusion under this Maintenance Agreement.

3.9  For certain WPS Software problems AGCS may require that BCGI furnish to
     AGCS a test case and sufficient documentation to allow recreation of the
     WPS Software problem.

4.   Unsatisfactory Condition Situation(s)

4.1  If at any time during normal operations AGCS encounters an unsatisfactory
     condition (noncompliance with the Related Documentation) directly related
     to the WPS Software, AGCS agrees to meet the following time frames for
     resolving the condition.

     (a) Conditions that affect the ability to track and collect revenue, or
     that cause major degradation of the WPS Software, requires a continuous
     effort until corrected, and provide a permanent resolution within fifteen
     (15) days of notification.

     (b) Conditions that affect service, but have a temporary solution to reduce
     the impact, or that have potential for major service degradation, AGCS
     shall acknowledge the condition within five (5) days of notification and
     will provide a permanent resolution within thirty (30) days of
     notification.

     (c) Conditions that are not service affecting but that have potential to
     adversely affect normal maintenance and/or administration or WPS Software
     service, AGCS will acknowledge the condition and provide a permanent
     resolution within sixty (60) days of notification.

4.2  BCGI and AGCS may agree to action dates to correct unsatisfactory
     conditions other than those mentioned above. The term "permanent
     resolution" shall mean a correction of an unsatisfactory condition in the
     form of a Modification and/or revised operating or maintenance procedures
     that are acceptable to BCGI and AGCS.

5.   EXCLUDED SERVICES

5.1  MAINTENANCE SERVICE DOES NOT INCLUDE:  (1) SERVICES CONNECTED WITH
     RELOCATION OR NETWORK RECONFIGURATION; (2) SERVICE RESULTING FROM:  (a)
     NEGLECT, MISUSE OR ACCIDENTAL DAMAGE OF THE WPS SOFTWARE (b) MODIFICATIONS
     OR REPAIRS PERFORMED BY OTHER THAN A PARTY AUTHORIZED BY AGCS; (c)
     CORRECTION OF DEFECTS ARISING FROM THE FAILURE OF BCGI TO PROVIDE AND
     MAINTAIN A SUITABLE INSTALLATION ENVIRONMENT INCLUDING BUT NOT LIMITED TO
     PROPER ELECTRICAL POWER, AIR CONDITIONING OR HUMIDITY CONTROL; OR (d) THE
     SUPPORT OF THE WPS SOFTWARE USED FOR OTHER THAN THE PURPOSES FOR WHICH THEY
     WHERE DESIGNED; (3) THE SUPPORT OF SOFTWARE DEVELOPED BY BCGI OR OBTAINED
     FROM THIRD PARTIES; OR (4) THE SUPPORT OF WPS SOFTWARE NOT PROVIDED BY
     AGCS.

6.   TERM AND TERMINATION

6.1  The initial maintenance term shall be the first twelve (12) months
     following the end of the warranty period provided by BCGI to the Service
     Provider.  At the end of this initial twelve (12) month maintenance term,
     maintenance shall automatically be renewed for the WPS Software for one-
     year renewal terms until
                                       3
<PAGE>

    Confidential Materials omitted and filed with the Securities and Exchange
    Commission.
                          Asterisks denote omissions.

     terminated by BCGI by giving AGCS notification in writing at least sixty
     (60) days prior to the expiration date of the existing maintenance term.

6.2  This Maintenance Agreement may be terminated upon the occurrence of one or
     more of the following events; provided, however, the terminating party
     shall have no liability to the other party for the exercise of any rights
     granted in this Article, nor shall such exercise have the effect of waiving
     any rights, claims, or damages to which the terminating party might be
     entitled.

     6.2.1  By AGCS if BCGI fails to pay the maintenance fees or any other
          amounts due hereunder within thirty (30) days of notice of failure to
          pay.

     6.2.2  By either party if the other party is in default of any other
          provision of the Agreement or this Maintenance Agreement, provided
          written notice of such alleged default has been given to the other
          party and such other party has not cured such default within thirty
          (30) days after receipt of such notice.  In the event maintenance
          services are terminated for any reason during any period covered by a
          prepaid maintenance fee, Service Provider shall be entitled to a
          refund of the prepaid and unused maintenance fees determined by
          dividing the annual maintenance fee by twelve (12) and multiplying the
          result by the number of months remaining in that maintenance period.
          The refundable amount applies only to prepaid amounts from Article 6
          and shall not apply to other amounts owed to AGCS by BCGI under any
          other provision of the Agreement or this Maintenance Agreement.

     6.2.3  By AGCS, if BCGI fails to keep current with updates to the WPS
          Software provided by AGCS.  "Keep current" shall be defined as the
          then current commercial release or one release prior (e.g., current =
          release 3.0, prior = release 2.0).

7.  MAINTENANCE CHARGES

7.1  System Sales.  For System Sales the price for the maintenance to be
     ------------
     provided to BCGI by AGCS under this Maintenance Agreement (except for
     maintenance to the Roaming Application and for service bureau usage) will
     be [**] of the WPS Software license fees if BCGI provides first level
     support and [**] of the WPS Software license fees if BCGI provides second
     level support.  This fee will be invoiced quarterly by AGCS beginning
     thirty (30) days prior to the expiration of the existing warranty or
     maintenance period, payable thirty (30) days from invoice date.  AGCS
     reserves the right to adjust the maintenance price for any renewal of this
     Maintenance Agreement upon ninety (90) days written notice prior to the end
     of the term then in effect up to an annual maximum increase of ten percent
     (10%).

7.2  Service Bureau. The price for maintenance to be provided to BCGI by AGCS
     --------------
     when BCGI is operating the WPS Software (except the Roaming Application and
     System Sales) in a service bureau environment is outlined in Section 7 of
     Amendment No. 1 of the Agreement.

7.3  Roaming Application. Maintenance of the Roaming Application is included in
     -------------------
     the License fees paid by BCGI to AGCS for such application until December
     31, 2001.

8.   ADDITIONAL SERVICES

8.1  Maintenance service beyond the scope of this Maintenance Agreement shall
     only be provided in response to a written request by BCGI and will be
     billed to BCGI at a mutually agreed to rate.

8.2  Software maintenance shall include coverage for Modifications by AGCS to
     BCGI during the maintenance term at no additional charge.
                                       4
<PAGE>

8.3  Software maintenance provided by AGCS to BCGI to support a Software
     Environment Upgrade during the maintenance term will be made available at a
     mutually agreed to rate. A Software Environment Upgrade is the updating of
     the WPS Software, or parts thereof, to permit the WPS Software to continue
     to operate according to its requirements and is made necessary by changes
     or modifications made to the computer platform on which the WPS Software
     operates.

8.4  Significant changes by BCGI to platform hardware and/or software such as
     additions or deletions of Operating System, disk interface utilities,
     process monitoring and control utilities, TCP/IP or HTTP web server require
     support effort not covered under this Maintenance Agreement. In the event
     significant changes are made to the Software Environment by BCGI, required
     changes to the WPS Software by AGCS will be treated as new development
     effort.

8.5  If AGCS performs maintenance service at BCGI's request for WPS Software
     that is no longer under warranty due to failure to extend or renew the
     warranty, failure to pay the applicable extended warranty fees or for any
     other out-of- warranty condition, those services shall be in response to a
     request therefor by BCGI in a written order and will be billed to BCGI at
     AGCS' then current charges for the services.


9.   TAXES

9.1  BCGI shall be responsible for all federal, state and local taxes and other
     governmental assessments arising from or based upon the maintenance charges
     payable under this Maintenance Agreement, however designated, exclusive of
     taxes on AGCS' net income. Such taxes and any other governmental
     assessments shall be added to AGCS' invoice to BCGI and remitted to the
     proper authorities by AGCS.

10.  DELAY

10.1 AGCS shall not be responsible for failure to render service hereunder or
     for delay in rendering such service where the failure or delay results from
     events of Force Majeure as defined in Section 19 of the Agreement.

11.  ASSIGNMENT

11.1 This Maintenance Agreement may not be assigned by either party without the
     prior written consent of the other party except as otherwise provided for
     under Assignments in the Agreement.

12.  DISCLAIMER OF WARRANTY

12.1 OTHER THAN THE WARRANTY PROVIDED FOR IN THIS MAINTENANCE AGREEMENT, AGCS
     MAKES NO WARRANTY, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
     ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE RELATED
     TO THE SERVICES TO BE PROVIDED HEREUNDER.

13.  LIMITATION OF LIABILITY

13.1 AGCS' LIABILITY UNDER THIS MAINTENANCE AGREEMENT SHALL BE LIMITED, AT AGCS'
     OPTION, TO THE SUPPORT, REPAIR OR REPLACEMENT OF THE SOFTWARE COVERED BY
     THIS MAINTENANCE AGREEMENT OR TO AN AMOUNT NOT TO EXCEED THE CURRENT ANNUAL
     CHARGES PAID UNDER THIS MAINTENANCE AGREEMENT FOR THE SOFTWARE IN QUESTION.
     IN NO EVENT SHALL AGCS BE LIABLE FOR INDIRECT, SPECIAL, INCIDENTAL OR
     CONSEQUENTIAL DAMAGES (INCLUDING LOSS OF PROFITS) WHETHER BASED ON
     CONTRACT, TORT OR ANY OTHER LEGAL THEORY.

14.  GENERAL

                                       5
<PAGE>

14.1 No term of this Maintenance Agreement shall be considered waived, and no
     breach excused, by either party unless made in writing.  No consent, waiver
     or excuse by either party, whether express or implied, shall constitute a
     subsequent consent, waiver or excuse.

14.2 If any provision of this Maintenance Agreement is held by a court of
     competent jurisdiction to be invalid or unenforceable such provision shall
     be severed from this Maintenance Agreement and the remaining provisions
     will remain in full force and effect.


IN WITNESS WHEREOF, the parties hereto have executed this Maintenance Agreement
and caused it to be effective on the date first written above.

CELLULAR EXPRESS, INC.                  AG COMMUNICATION SYSTEMS
                                        CORPORATION
By: /s/ Kevin Thigpen                   By: /s/ Charles Schulz
  ----------------------------            ----------------------------

Name: Kevin Thigpen                     Name: Charles Schulz
     -------------------------               -------------------------

Title: Vice President
       & General Manager                Title: VP/GM PAG
     -------------------------               -------------------------

Date: August 24, 1999                   Date: August 26, 1999
    --------------------------              --------------------------

                                       6