<PAGE>
 
                                                                   Exhibit 10.37
                                                                   -------------
SECTION 0:  SIGNATURE PAGE
            --------------

         THIS CARRIER AGREEMENT ("Agreement") is made and entered into by and
between AT&T Corp., a corporation organized and existing under the laws of the
State of New York and having an office at 295 North Maple Avenue, Basking Ridge,
New Jersey 07920 ("AT&T") and Boston Communications Group Inc., having an office
at 100 Sylvan Rd., Woburn, MA 01801 ("Customer").  The terms and conditions
herein constitute an offer by Customer as of the date of Customer's signature
below which may be accepted only by AT&T's signature below.  This Agreement
shall become effective when signed by both parties.

   AT&T and Customer, acting through their duly authorized representatives,
hereby agree to the terms set forth in Sections 1 through 6 of this Agreement as
attached hereto.



CUSTOMER                                AT&T CORP.

By                                      By 
   ------------------------------          ----------------------------

   Robert J. Sullivan                       David Karlin
---------------------------------       -------------------------------
Printed or Typed Name                   Printer or Typed Name

   Vice President                           Senior Sales Manager
---------------------------------       -------------------------------
Title                                   Title

   7/10/97                                  7/14/97
---------------------------------       -------------------------------
Date                                    Date

                                       3

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
SECTION 1:  GENERAL TERMS AND CONDITIONS
            ----------------------------

1.A.  Assignment.  Customer may not assign this Agreement in whole or in part
      -----------                                                            
      without the prior written consent of AT&T, which shall not be unreasonably
      withheld. AT&T may, in its discretion, condition its consent to such
      assignment upon the posting of an appropriate deposit by the assignee
      pursuant to Paragraph 4.D. of this Agreement. AT&T reserves the right to
      deny or revoke its consent to such assignment at any time if the assignee
      proves unwilling or unable to meet the eligibility requirements of this
      Agreement, in which event the Customer shall remain or again become
      responsible for performance of all terms of this Agreement. This provision
      shall not affect the Customer's right to resell Service. Further, any
      resale or assignment shall not release the original Customer from its
      obligations under this Agreement. 

1.B.  Combination with Other Services or Offers. This AT&T Carrier Agreement
      ------------------------------------------                             
      may not be used in conjunction with any other AT&T Carrier Agreement, AT&T
      Contract Tariff, or promotions for any AT&T Services.

1.C.  Independent Parties.  The relationship established by this Agreement shall
      --------------------                                                      
      in no way constitute AT&T (or its agents or employees) as a partner, agent
      or fiduciary of Customer. The relationship established by this Agreement
      shall in no way constitute the Customer (or their agents or employees) as
      a partner, agent or fiduciary of AT&T. The provision of Service described
      in this Agreement does not establish any joint undertaking, joint venture,
      or fiduciary relationship between AT&T and Customer.

1.D.  Acknowledgment of Right to Compete.  Customer acknowledges and understands
      -----------------------------------                                       
      that it remains at all times solely responsible for the success and
      profits of its business, and that AT&T makes no promises, warranties or
      representations regarding the Customer's business success or prospects of
      business success in connection with the provision of service pursuant to
      this Agreement, Customer acknowledges and understands that AT&T will
      continue to market AT&T services directly to the public and that such
      marketing may from time to time bring AT&T into direct or indirect
      competition with Customer, and that AT&T may also market its services to
      competitors of Customer. Customer acknowledges and understands that
      nothing in this Agreement diminishes or restricts in any way the fights of
      AT&T to engage in competition with Customer or to market its services to
      competitors of Customer.

1.E.  Use of Proprietary Information.  In the event that either Customer or
      -------------------------------                                      
      AT&T, in the course of performance of their obligations to each other
      under this Agreement, obtains or receives proprietary information from the
      other, it agrees to use such information only for the purpose of complying
      with its obligations under this Agreement and not to use such information
      for its own marketing purposes, Customer acknowledges that AT&T may use
      for its own marketing purposes any and all information that it obtains
      from sources other

                                       4

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
      than Customer, including but not limited to information that AT&T may have
      regarding Customer's End-Users as a result of the past or present sale or
      provision by AT&T of telecommunications services or equipment to said End-
      Users.

1.F.  Force Majeure.  Neither party nor its affiliates, subsidiaries,
      --------------                                                 
      subcontractors, or parent corporation shall be liable in any way for
      delay, failure in performance, loss or damage due to any of the following:
      fire, strike, embargo, explosion, power blackout, earthquake, volcanic
      action, flood, war, water, the elements, labor disputes, civil or military
      authority, acts of God, acts of the public enemy, inability to secure raw
      materials, inability to secure products, acts or omissions of carriers, or
      other causes beyond its reasonable control, whether or not similar to the
      foregoing.

1.G.  Severability.  If any portion of this Agreement shall be found to be
      -------------                                                       
      invalid or unenforceable, such portion shall be void and of no effect, but
      the remainder of the Agreement shall continue in full force and effect
      unless the Agreement fails of its essential purpose without the voided
      portion.

1.H.  Notices.  All notices, identifications, formal requests or other formal
      --------                                                               
      communications required or desired to be given in connection with this
      Agreement, shall be in writing and shall be effective when delivered in
      person, mailed by registered or certified post or sent by Telex or
      facsimile ("FAX") to the recipient party, unless the parties otherwise
      agree in writing.  Notice shall be addressed to the following:

      If to AT&T:      Senior Sales Manager
                       AT&T Corner Solutions
                       4513 Western Avenue, Room 121
                       Lisle, IL  60532

      If to Customer:  100 Sylvan Road
                       Woburn, MA  01801

                                       5

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
1.I.  Modification And Waiver.  This Agreement may be modified only by a writing
      -----------------------                                                   
      signed by both parties.  The failure of a party to enforce any right under
      this Agreement at any particular point in time shall not constitute a
      continuing waiver of any such right with respect to the remaining term of
      this Agreement, or the waiver of any other right under this Agreement.

1.J.  Compliance with Laws.  Each party is responsible for its own compliance
      --------------------                                                   
      with all laws and regulations affecting its business, including but not
      limited to the collection and remittance of all taxes and other levies
      imposed by law.

1.K.  Choice of Law.  The domestic law of the State of New York, except its
      -------------                                                        
      conflict-of-laws rules, shall govern the construction, interpretation, and
      performance of this Agreement.

1.L.  Confidentiality.  The Terms, conditions, and rates contained in this
      ----------------                                                    
      Agreement are confidential, and shall remain so unless and until it shall
      be determined by AT&T that the Communications Act of 1934 (or any
      subsequent legislation) and the regulations promulgated thereunder require
      the filing of this Agreement with the Federal Communications Commission
      ("Commission"), or unless the Commission orders the filing of this
      Agreement pursuant to authority granted to the Commission by law or
      regulation. In such event, AT&T shall file the Agreement within thirty
      days of its execution, or upon such determination that filing is required,
      or upon being ordered by the Commission to do so (whichever is later),
      provided, that AT&T nonetheless shall keep the identity of Customer
      confidential unless required by law, regulation or the Commission to
      disclose such identity. Absent such a filing requirement, neither party
      shall disclose the terms or conditions of this Agreement to any third
      party, nor issue any public statements relating to this Agreement without
      the written consent of the other party, unless such disclosure or
      statement is reasonably believed by the party to be compelled by
      governmental authority. A disclosing party shall furnish reasonable prior
      notice to the other party before making the statement or disclosure unless
      prohibited by law from doing so.

1.M.  Dispute Resolution.  If a dispute arises out of or relates to this
      -------------------                                               
      Agreement, or its breach, the parties agree to submit the dispute to a
      sole mediator selected by the parties or, at any time at the option of a
      party, to mediation by the American Arbitration Association ("AAA"), to be
      held in Morristown, New Jersey, If not resolved by mediation, it shall be
      referred to a sole arbitrator selected by the parties within thirty (30)
      days of the mediation or, in the absence of such selection, to AAA
      arbitration which shall be governed by the United States Arbitration Act
      and judgment on the award may be entered in any court having jurisdiction.
      The arbitrator may not limit, expand or otherwise modify the terms of this
      Agreement. The parties, their representatives, other participants and the
      mediator and arbitrator shall hold the existence, content and results of
      mediation and arbitration in confidence.

                                       6

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
1.N.  Trade Names, Trademarks, Service Marks and Registered Marks   Neither
      -----------------------------------------------------------          
      Customer nor AT&T shall use the other's trade names, trademarks or service
      marks ("Marks") without the prior written approval of the other party.
      Neither shall display or use the other's Marks, nor pen-nit the same to be
      displayed or used by third parties. Nothing in this Agreement creates in a
      party rights in the Marks of the other.

1.O.  Entire Agreement.  This Agreement constitutes the entire agreement of the
      -----------------                                                        
      parties with respect to the subject matter hereof and supersedes all prior
      written or oral agreements, proposals or understandings.
 
1.P.  Definitions. As used in this Agreement, the definitions set forth in AT&T
      -------------                                                            
      Tariff F.C.C. Nos. 1, 2, 9 and 11 shall apply except to the extent that
      they are modified or supplemented as follows:

      1.P.1.  End-Users:  Those persons or entities to which Customer provides
              ---------                                                       
      service as a telecommunications common carrier utilizing the service
      provided to Customer by AT&T pursuant to this Agreement,

      1.P.2.  Dispute:  Any controversy or claim between the parties under this
              -------                                                          
      Agreement or which relates directly or indirectly to this Agreement or the
      services provided hereunder, whether based on contract, product liability,
      statute, tort (including negligence or strict liability) or other legal or
      equitable theory, whenever brought, between the parties or any of their
      employees or agents.

      1.P.3.  CISD:  The date for commencement of installation of Service
              ----                                                       
      established pursuant to Paragraph 3.B. of this Agreement.
 
      1.P.4.  Customer Premises:  An IXC Switch location as specified in Section
              -----------------                                                 
      6.C.1. of this Carrier Agreement.

      1.P.5. Tariffs: As used in this Agreement, the term "tariffs" "Applicable
             -------
      Tariffs," or any variation thereof shall mean AT&T Tariff F.C.C. Nos. 1,
      2, 9, and 14, in effect on the effective date of this Agreement and any
      subsequent revisions to such AT&T tariff services provided pursuant to
      this Agreement.

                                       7

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
SECTION 2:  REQUIREMENTS AND CERTIFICATION OF ELIGIBILITY
            ---------------------------------------------


2.A.    Eligibility.  The rates, terms and conditions herein are expressly
        -----------                                                       
        conditioned upon the Customer's meeting the following eligibility
        requirements.  Customer is an interexchange telecommunications common
        carrier which certifies as follows:

2.A.1.  Customer has obtained the required operating authority in all states in
        which it conducts business, as well as all authority required by the FCC
        for resale of telecommunications services, including but not limited to
        authority required pursuant to Section 214 of the Communications Act of
        1934, 47 U.S.C. (S)214.

2.A.2.  Customer complies and will continue to comply at all times with all
        federal and state laws and regulations applicable to the sale and
        provision of service to its customers, including but not limited to
        those laws and regulations applicable to the authorization and proof of
        authorization necessary to convert an End-Users former service to
        Customer's service as the End-User's Primary Interexchange Carrier.

2.A.3.  Customer has and uses its own carrier identification code ("CIC") in
        connection with the origination of all traffic routed via Service
        provided under this Agreement. Customer is solely responsible for
        installation of its CIC in all access provider end offices (including
        Local Exchange Carrier end offices), and for the payment of all charges
        associated therewith, including but not limited to charges for
        transmission of Customer's CIC to AT&T.

2.A.4.  Customer has had a consistent on-time payment record with respect to all
        telecommunications service to which it has subscribed with AT&T and all
        other telecommunications common carriers for at least 24 consecutive
        months prior to the execution of this Agreement. This requirement
        includes affiliates, parents, subsidiaries, predecessors and successors
        of Customer and any entity owned 20% or more by any person or entity
        which also has an ownership interest of 20% or more in Customer on the
        Effective Date.

2.A.5.  Customer will utilize the Service offered hereunder only for lawful
        purposes, including but not limited to resale of the Service or
        components thereof. In the event that Customer resells the Service
        provided hereunder, it will do so only under its own names, tradenames,
        logos, trademarks or servicemarks. Customer will not publish or use any
        advertising, sales promotions, press releases, or other publicity
        matters which use AT&T's corporate or trade names, logos, trademarks,
        service marks, trade dress, or other symbols that serve to identify and
        distinguish AT&T from its competitors (or which use confusingly similar
        corporate or trade names, logos, trademarks, service marks, trade dress
        or other symbols), and will not conduct business under AT&T's

                                       8

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
        corporate or trade names, logos, trademarks, service marks, trade dress,
        or other symbols that serve to identify and AT&T from its competitors
        (or under any confusingly similar corporate or trade names, logos,
        trademarks, service marks, trade dress or other symbols). Customer
        (including its agents, representatives and independent contractors) will
        not indicate or imply to any person or entity that it is AT&T which is
        selling or providing service to Customer's end-users, or that it is
        affiliated or authorized by AT&T to sell or provide such service to them
        or that it is selling or providing such service to them jointly or in
        collaboration or partnership with AT&T, or as the agent of AT&T.

2.A.6.  Customer has had no complaints or proceedings brought against it, within
        two months prior to its execution of this Agreement, by the FCC, by any
        state public utilities commission, by any state Attorney General, or by
        any other federal or state authority charging Customer with
        misrepresenting its affiliation or relationship to AT&T or to any other
        carrier whose service it has resold, and no such complaints or
        proceedings are pending as of Customer's execution of this Agreement.

2.B.    Termination for Lack of Eligibility.  If at any time during the term of
        -----------------------------------                                    
        this Agreement Customer fails to comply with any requirement for
        eligibility contained in Paragraphs 2.A.1 through 2.A.6., above, such
        failure shall constitute a material breach of this Agreement which shall
        entitle AT&T to terminate this Agreement and the Service provided
        hereunder on thirty (30) days written notice. Customer shall have the
        opportunity to cure such failure during the thirty (30) day period
        following such notice, and, if such cure is demonstrated to the
        satisfaction of AT&T, no termination pursuant to this Paragraph shall
        occur. In the event of such termination, Customer shall indemnify,
        defend and hold harmless AT&T from any and all complaints, causes or
        action or other claims brought against AT&T by any of Customer's End-
        Users due to said termination.

2.C.    Default.  If at any time during the term of this Agreement either party
        -------                                                                
        shall commit an act of bankruptcy within the meaning of the United
        States Federal Bankruptcy Act, or bankruptcy, receivership, insolvency,
        reorganization, dissolution, liquidation, or other proceedings shall be
        instituted by or against either party or all or any substantial part of
        its property under an applicable law of the United States or any state
        thereof, and such proceeding shall not be dismissed within ninety (90)
        calendar days, the non-defaulting party shall have the right to
        terminate this Agreement.

                                       9

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
SECTION 3:  RESPONSIBILITIES OF AT&T
            ------------------------

3.A.  Provision of Service.  Subject to its Correspondent Agreements and
      --------------------                                              
      regulation by Federal and state authorities, AT&T shall provide Service in
      accordance with its standard practices and procedures for the operation of
      its network.  Service shall be available 24 hours per day, seven days per
      week. AT&T is responsible for the provision of Service from station to
      station, but is not responsible for the quality of transmission or
      signaling on the Customer's side of the interface at a Customer's
      premises. Service is furnished subject to the availability of the service
      components required. AT&T will determine which of those components shall
      be used and make modifications to those components at its option.

3.B.  Installation.  Upon execution of this Agreement AT&T shall establish a due
      ------------                                                              
      date for commencement of installation of Service and confirm said date
      with the Customer (CISD). A Customer may delay said due date for
      commencement of installation when the Customer's written request for said
      delay is received by AT&T at least five (5) business days prior to said
      due date, provided that the delay of said due date shall not exceed 30
      cumulative calendar days. AT&T will make every reasonable effort to
      commence installation of Service by the due date, but Customer
      acknowledges that in some cases a delay in commencement of installation
      may be unavoidable. If commencement of installation is delayed for more
      than 45 days beyond the due date, and such delay is not requested or
      caused in whole or in part by the Customer, the Customer may cancel its
      order for Service pursuant to this Agreement and shall not thereby be
      considered to have breached this Agreement; such cancellation shall he
      Customer's sole remedy for such delay.

3.C.  Maintenance.  AT&T shall maintain Service in conformity with its standard
      -----------                                                              
      network operating procedures.

3.D.  Limitation of Liability.  AT&T (INCLUDING ITS SUBSIDIARIES, AFFILIATES,
      -----------------------                                                
      PREDECESSORS, SUCCESSORS AND ASSIGNS) MAKES NO WARRANTIES, EXPRESS OR
      IMPLIED, AND SPECIFICALLY DISCLAIMS ANY WARRANTY OF MERCHANTABILITY OR
      FITNESS FOR A PARTICULAR PURPOSE WITH RESPECT TO SERVICES OR PRODUCTS
      PROVIDED PURSUANT TO THIS AGREEMENT. AT&T'S LIABILITY FOR SERVICE
      INTERRUPTIONS FOR ANY SERVICE PROVIDED PURSUANT TO THIS AGREEMENT SHALL
      NOT EXCEED AN AMOUNT EQUAL TO A PRO-RATED PORTION OF THE RECURRING CHARGES
      PROVIDED FOR UNDER THIS AGREEMENT FOR THE SERVICE AFFECTED FOR THE
      PERIOD(S) DURING WHICH SAID SERVICE WAS AFFECTED. THIS LIMITATION OF
      LIABILITY SHALL APPLY REGARDLESS OF THE FORM OF ACTION, WHETHER IN
      CONTRACT, TORT, WARRANTY, STRICT LIABILITY, OR NEGLIGENCE (INCLUDING
      WITHOUT LIMITATION

                                      10

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
      ACTIVE AND PASSIVE NEGLIGENCE). IN NO EVENT SHALL AT&T BE LIABLE FOR
      CONSEQUENTIAL, SPECIAL OR INDIRECT DAMAGES OR LOST PROFITS SUSTAINED BY
      REASON OF ITS PERFORMANCE OF THIS AGREEMENT, OR FOR ANY FAILURE,
      BREAKDOWN, OR INTERRUPTION OF SERVICE, WHATEVER SHALL BE THE CAUSE, OR
      HOWEVER LONG IT SHALL LAST, AND REGARDLESS OF WHETHER ANYONE HAS BEEN
      ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. AT&T SHALL HAVE NO LIABILITY
      FOR DAMAGES CAUSED (1) BY CUSTOMER'S FAILURE TO PERFORM ITS
      RESPONSIBILITIES UNDER THIS AGREEMENT, OR (2) BY THE ACTS OF THIRD PARTIES
      (INCLUDING WITHOUT LIMITATION CUSTOMER'S USERS OR END USERS). AT&T DOES
      NOT GUARANTEE OR MAKE ANY WARRANTY WITH RESPECT TO THE SERVICE PROVIDED
      PURSUANT TO THIS AGREEMENT WHEN USED IN AN EXPLOSIVE ATMOSPHERE. THIS
      AGREEMENT DOES NOT CREATE ANY CLAIM OR RIGHT OF ACTION, NOR IS IT INTENDED
      TO CONFER ANY BENEFIT ON ANY THIRD PARTY, INCLUDING BUT NOT LIMITED TO ANY
      USER OR END-USER OF CUSTOMER. THE LIMITATIONS OF LIABILITY SET FORTH IN
      THIS AGREEMENT SHALL SURVIVE FAILURE OF AN EXCLUSIVE REMEDY.

3.F.  Service, Channels or Equipment of Others.  AT&T is not liable for damages
      ----------------------------------------                                 
      associated with service, channels, or equipment that it does not furnish.
      AT&T does not provide Customer equipment.

3.G.  No Patent or Software License.  No license under patents or software
      -----------------------------                                       
      copyrights (other than the limited license to use) is granted by AT&T or
      shall be implied or arise by estoppel, with respect to Service offered
      under this Agreement.

                                      11

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
SECTION 4:  RESPONSIBILITIES OF CUSTOMER
            ----------------------------

4.A.  Placement of Orders and Compliance with Regulations.  Customer is
      ----------------------------------------------------             
      responsible for placing any necessary orders and for assuring that it, its
      Users and its End-Users comply with the provisions of this Agreement and
      with all applicable federal and state laws and regulations.

4.B.  Billing; Responsibility for Payment.  Customer is liable for all amounts
      ------------------------------------                                    
      due to AT&T hereunder, subject to the following. AT&T will provide to
      Customer a single monthly bill for each of the Services provided under
      this Agreement, or at AT&T's option a single monthly bill for all of the
      Services provided under this Agreement. Said bill or bills will be sent to
      one Customer location designated by the Customer. Payment of charges is
      due upon presentation of a bill unless a different due date appears on the
      face of the bill, in which case payment shall be due on said date.
      Customer shall be solely responsible for rendering of bills to and
      collection of charges from its end-users. Failure of Customer to bill and
      collect charges from its end-users shall not excuse in whole or in part
      Customer's responsibilities to AT&T under this Agreement, including but
      not limited to the responsibility to render to AT&T timely payment of
      charges. Customer shall reimburse AT&T for reasonable attorneys fees and
      any other costs associated with collecting delinquent payments from
      Customer. At AT&T's option, interest charges may be added to any
      undisputed adjudged past due amounts at the rate of one and one-half
      percent (1 1/2%) per month, unless such interest rate exceeds the maximum
      allowed by applicable law, in which case interest shall be at the maximum
      lawful rate.

4.C.  Interfacing and Communicating with End-Users.  Interfacing and
      ---------------------------------------------                 
      communicating with End-Users shall be the sole responsibility of Customer
      with respect to any use that Customer may make of the service provided
      pursuant to this Agreement to in turn provide service to other persons or
      entities.  Such interfacing and communicating shall include without
      rotation installation of service, termination of service, placing of
      orders, billing and billing inquiries, reporting of service outages and
      problems, collection of charges and handling and resolution of all
      disputes.

4.D.  Deposits.  AT&T may require the Customer, prior to or during the provision
      --------                                                                  
      of service pursuant to this Agreement, to tender a deposit in an amount to
      be determined by AT&T in its reasonable discretion to be held by AT&T as a
      guarantee for the payment of charges (including but not limited to
      shortfall charges attributable to Customer's failure to comply with any
      revenue or volume commitment or any monitoring condition in this
      Agreement).  To determine the financial responsibility of Customer and/or
      the specific amount of any deposit required, AT&T may rely upon
      commercially reasonable factors to assess and manage the risk of non-
      payment, including but not limited to payment history for
      telecommunications service (including such service purchased from AT&T),
      number of years in business, bankruptcy or insolvency history, current
      AT&T account treatment

                                      12

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
      status, financial statement analysis, and commercial credit bureau rating.
      It shall be Customer's responsibility to provide to AT&T upon request such
      information as is necessary for AT&T to determine the financial
      responsibility of Customer, including but not limited to Customer's tax
      returns, audited or unaudited financial statements and loan applications.
      A deposit does not relieve Customer of the responsibility for the prompt
      payment of bills on presentation or the due date appearing on the face of
      the bills. In lieu of a cash deposit, AT&T will accept Bank Letters of
      Credit and Surety Bonds which have been approved by AT&T. Interest will be
      paid to a Customer for the period that a cash deposit is held by AT&T. The
      interest rate used will be simple interest at the rate of six percent
      annually unless a different rate has been established by the appropriate
      legal authority in the state where the Service offering is located. The
      failure of Customer to post a deposit as required by AT&T pursuant to this
      paragraph shall constitute a material breach of this Agreement by Customer
      which shall entitle AT&T to terminate this Agreement and the service
      provided hereunder upon five (5) days written notice to Customer. When the
      service for which the deposit has been required is discontinued, the
      deposit will be applied to the final bill and any credit balance will be
      refunded to the Customer with applicable interest accrued.

4.E.  Customer's Use of Service.  Customer may use the services provided
      --------------------------                                        
      pursuant to this Agreement for any lawful purpose consistent with the
      transmission and switching parameters of the telecommunications network,
      and may resell its use (or the use of any part thereof) to a third party
      in the normal course of the Customer's business, subject to the 
      following-.

      4.E.1.  Abuse - The abuse of Service is prohibited.  The Following
              -----                                                     
      activities constitute abuse:

      4.E.1.A.  Using Service to make calls that might reasonably be expected to
      frighten, abuse, torment, or harass another, or

      4.E.1.B.  Using Service in such a way that it interferes unreasonably with
      the use of Service or AT&T's network by others.

      In any instance in which AT&T believes in good faith that there is abuse
      of Service as set forth above, AT&T may, upon 5 days prior written notice
      to the Customer, and without liability on the part of AT&T, restrict,
      suspend or discontinue providing Service, unless Customer cures such abuse
      to AT&T's reasonable satisfaction within such period.

      4.E.2.  Fraudulent Use.  The fraudulent use of, or the intended or
              --------------                                            
      attempted fraudulent use of, Service is prohibited.  The following
      activities constitute fraudulent use:

                                      13

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
           4.E.2.A.  Using Service to transmit any message or code, locate a
           person, or otherwise give or obtain information, without payment for
           Service, or

           4.E.2.B.  Using or attempting to use Service with the intent to avoid
           the payment, either in whole or in part, of any charges by any means
           or device, or

           4.E.2.C.  Using Service to carry calls that originate on the network
           of a facilities-based interexchange carrier other than AT&T and
           terminate disproportionately to locations for which the cost to AT&T
           of terminating switched access is above the average cost of
           terminating switched access, based on the published access tariffs of
           local exchange companies.

           In any instance in which AT&T believes in good faith that there is
           fraudulent use of Service as set forth above, AT&T may, immediately
           and upon written notice to the Customer, and without liability on the
           part of AT&T, restrict, suspend or discontinue providing Service.

      4.E.3.  Interference, Impairment or Improper Use.  Customer may not use
              ----------------------------------------                       
      Service in any manner that subjects AT&T personnel or non-AT&T personnel
      to hazardous conditions or results in immediate harm to the AT&T network
      or other AT&T services. In any instance in which AT&T believes in good
      faith that Service is being used in such manner, AT&T may immediately
      restrict Service on a temporary basis. In such cases, AT&T will make a
      reasonable effort to give the Customer prior notice. In the event that
      Customer does not provide to AT&T within five (5) business days of the
      temporary restriction of service acceptable proof that said use has ceased
      and that appropriate measures have been taken to prevent its recurrence,
      AT&T may immediately and without further notice terminate service.

4.F.  Access to Customer's Premises.  The Customer is responsible for arranging
      -----------------------------                                            
      premises access at any reasonable time so that AT&T personnel may install,
      repair, maintain, inspect or remove Service components. Premises access
      must be made available at a time mutually agreeable to the Customer and
      AT&T.

4.G.  Loss.  The Customer is liable to AT&T for the replacement cost of AT&T-
      ----                                                                 
      provided equipment installed at the Customer's premises in the event of
      loss of said equipment for any reason, including but not limited to theft.

4.H.  Duty to Indemnify and Defend.  Customer shall indemnify, defend, and hold
      ----------------------------                                             
      harmless AT&T and its directors, officers, employees, agents, parent,
      subsidiaries, successors, and assigns from all claims, damages and
      expenses (including reasonable attorneys' fees) arising out of or
      resulting from, in whole or in part, the acts or omissions of Customer or
      its End-Users, their employees, agents or contractors affiliated companies
      and their employees, agents or contractors, including but not limited to
      claims for libel, slander,

                                      14

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
     invasion of privacy, or infringement of copyright arising from any
     communication and claims for patent infringement arising from combining or
     using services or equipment furnished by AT&T in connection with services
     or equipment furnished by others.  Customer shall also indemnify, defend
     and hold AT&T harmless for all causes of action, claims, liabilities or
     expenses asserted or incurred by any of Customer's Users or End-Users
     arising out of any failure, breakdown, or interruption of service provided
     to Customer by AT&T or to End-Users by Customer.  Customer shall indemnify,
     defend and hold AT&T harmless for all causes of action, claims, liabilities
     or expenses asserted or incurred by Customer's End-Users due to Customer's
     marketing efforts, including but not limited to Customer's violation of
     laws and regulations applicable to the authorization and proof of
     authorization necessary to convert an End-User's former service to
     Customer's service as the End-User's Primary Interexchange Carrier, AT&T
     shall be indemnified, defended, and held harmless by the Customer, Users
     and End-Users against all claims, losses, or damages by any person relating
     to such Service when used in an explosive atmosphere.

                                      15

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
SECTION 5:  SERVICES AND SERVICE DESCRIPTIONS
            ---------------------------------

5.A.  Domestic Interstate and International Services.  The following domestic
      -----------------------------------------------                        
      interstate and international services are provided pursuant to this
      Agreement:

      5.A.1.  AT&T MEGACOM(reg) Service - Domestic and International Calling
      Capability as described and defined in AT&T Tariff F.C.C. No. 1, as
      amended from time to time.

      5.A.2.  AT&T MEGACOM(reg) 800 Service (Domestic) as described and defined
      in AT&T Tariff F.C.C- No. 2, as amended from time to time.

      5.A.3. AT&T ACCUNET(reg) T1.5 Access Connections as described and defined
      in AT&T Tariff F.C.C. No. 9, as amended from time to time.

      5.A.4.  AT&T Terrestrial 1.544 Mbps Local Channel service as described and
      defined in AT&T Tariff F.C.C. No. 11, as amended from time to time.

5.B.  Domestic Intrastate Services.  The following intrastate services are
      -----------------------------                                       
      provided pursuant to AT&T's state tariffs governing such service:

      5.B.l.  AT&T MEGACOM Service - Domestic as described and defined in AT&T
      Tariff F.C.C. No. 1, as amended from time to time.

      5.B.2.  AT&T MEGACOM 800 Service (Domestic) as described and defined in
      AT&T Tariff F.C.C. No. 2, as amended from time to time.


                                      16

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
SECTION 6:  SERVICE RATES, TERMS AND CONDITIONS
            -----------------------------------

6.A.  Service Term.  The term of this Agreement is 12 months beginning with the
      -------------                                                            
      first day of the first full billing month within 30 days of the effective
      date of this Agreement (hereinafter referred to as the Customer's Initial
      Service Date, or ("CISD") for the Services provided under this Carrier
      Agreement.  There is no renewal option.

6.B.  Minimum Volume Commitments
      --------------------------

      6.8.1.

6.C.  Usage Rates.  AT&T reserves the right to increase from time to time the
      -----------                                                            
      rates for the Services Provided under this Agreement, regardless of any
      provisions in this Agreement that would otherwise stabilize rates or limit
      rate increases, as a result of charges imposed on AT&T stemming from an
      order, rule or regulation of the Federal Communications Commission or a
      court having competent jurisdiction relating to compensation of payphone
      service providers. If necessary, revisions will be filed in this Agreement
      to reflect the actual rates. The Contract Prices for the Services Provided
      pursuant to this Agreement are as follows:

      6.C.1. The Contract price for the AT&T MEGACOM Service provided under this
      Agreement is the same as the undiscounted Recurring and Nonrecurring Rates
      and Charges specified for said Service in AT&T Tariff F.C.C. No. 1, as
      amended from time to time, except that the following usage rate, and the
      discounts specified in Section 6.D. of this Agreement, applies for AT&T
      MEGACOM Service-Domestic Interstate calls which originate at an IXC
      Switch: The Contract Price for AT&T MEGACOM Service- Domestic Interstate
      Service is     for the initial 18 seconds and       for each additional 6
      seconds or fraction thereof for all day parts and mileage bands. An IXC
      Switch is a telecommunications switch with the following characteristics
      (a) it is owned and operated by the Customer; (b) it has the capability to
      be used for the transmission of calls that are routed by a Local Exchange
      Carrier to the IXC Switch using Feature Group D access; (c) it is capable
      of interconnecting circuits or transferring calling between circuits; (d)
      it has a capacity of at least 100,000 access lines; and (e) it is used by
      Customer to provide Common Carriage service to end-users.

      6.C.2.  The Contract price for the AT&T MEGACOM Service - International
      Calling Capability provided under this Agreement is the same as the
      undiscounted Recurring and Nonrecurring Rates and Charges specified for
      said Service in AT&T Tariff F.C.C. No. 1, as amended from time to time.

      6.C.3.  The Contract price for the AT&T MEGACOM 800-Domestic Interstate
      Service provided under this Agreement is the same as the undiscounted
      Recurring and

                                      17

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
      Nonrecurring Rates and Charges specified for said Service in AT&T Tariff
      F.C.C. No. 1, as amended from time to time, except that the following
      usage rate, and the discounts specified in Section 6.D. of this Agreement,
      applies for AT&T MEGACOM 800 Service-Domestic Interstate calls which
      originate at an IXC Switch: The Contract Price for AT&T MEGACOM 800
      Service-Domestic Interstate Service is $ per hour for all day parts and
      mileage bands. An IXC Switch is a telecommunications switch with the
      following characteristics: (a) it is owned and operated by the Customer;
      (b) it has the capability to be used for the transmission of calls that
      are routed by a Local Exchange Carrier to the IXC Switch using Feature
      Group D access; (c) it is capable of interconnecting circuits or
      transferring calling between circuits; (d) it has a capacity of at least
      100,000 access lines; and (e) it is used by Customer to provide Common
      Carriage service to end-users.

      6.C.4.  The Contract Price for ACCUNET T1.5 Access connection is the same
      as specified in AT&T Tariff F. C. C. No. 9, as amended from time to time.

      6.C.5.  The Contract Price for AT&T Terrestrial 1.544 Mbps Local Channel
      Service is the same as specified in AT&T Tariff F. C. C. No. 11, as
      amended from time to time.

6.D.  Discounts.  Volume discounts applicable to the services provided pursuant
      ---------                                                                
      to this Agreement are as follows:

      6.D.1. The customer will receive one of the following tiered monthly
      discounts for AT&T MEGACOM Service - domestic gross usage in lieu of any
      other term plan or discounts.

      Monthly Domestic Gross Revenue            Discount
      ------------------------------            --------


      6.D.2. AT&T MEGACOM Services International Calling Capability as provided
      under this Agreement: The customer will receive the following monthly
      discounts for AT&T MEGACOM Services -International Calling Capability
      gross usage in lieu of any other term plan or discounts.

      Monthly International Gross Revenue         Discounts
      -----------------------------------         ---------

      6.D.3. The customer will receive one of the following tiered monthly
      discounts for AT&T MEGACOM 800 Service - domestic gross usage in lieu of
      any other term plan or discounts.

      Monthly Domestic Gross Revenue               Discount
      ------------------------------               --------

                                      18

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
6.E.  Additional Discounts, Credits, Waivers.
      -------------------------------------- 

      6.E.1.

      6.E.2.

      6.E.3.

6.F.  Classifications, Practices and Regulations.  Except as otherwise
      -------------------------------------------                     
      provided in this Agreement, the terms, conditions, regulations and charges
      for AT&T MEGACOM Service and International Calling Capability as set forth
      in AT&T Tariff F. C. C. No 1; for AT&T MEGACOM 800 Service as set forth in
      AT&T Tariff F. C. C. No 2, for Service Access Connections as w forth in
      AT&T Tariff F. C. C. No. 9; and for AT&T Terrestrial 1.544 Mbps Local
      Channel Service as set forth in AT&T Tariff F. C. C. No 11 apply, as these
      tariffs may be amended from time to time.

      6.F.1. The Customer may include usage from multiple Customer Premises to
      satisfy its volume commitments and qualify for discounts.

6.G.  Monitoring Conditions.  The Customer must satisfy the following Service
      ----------------------                                                 
      Requirements which will be monitored on each anniversary of the CISD.  The
      Monitoring Period is the 12 months immediately preceding each anniversary
      of the CISD.

      6.G.1.  At least   % of the Customer's AT&T MEGACOM Service and AT&T
      MEGACOM 800 Service domestic usage provided under this Agreement,
      following CISD, must be interstate minutes of use.

      6.G.2. The Customer must have an Average Length of Call (ALOC) of at least
      minutes each for AT&T MEGACOM Service and AT&T MEGACOM 800 Service calls.

      If the Customer, during the Monitoring Period, has failed to satisfy any
      of the above Monitoring Conditions, AT&T will notify the Customer in
      writing of the specific failure(s) and the Customer will be billed and
      shall pay within 30 days an amount equal to 20% of all usage billed for
      the service to which each unfulfilled Monitoring Condition is applicable
      during the Monitoring Period.

6.H.  Discontinuance - In lieu of any Discontinuance With or Without Liability
      ---------------                                                         
      provisions that are specified in the AT&T Tariff F.C.C. Nos. 1, 2, 9, 11
      and 14 the following provisions shall apply.

      6.H.l.  Discontinuance Without Termination Liability.  The Customer may
              --------------------------------------------                   
      discontinue this Agreement without incurring a Termination Charge as
      defined in Paragraph 6.I., below, prior to the end of the Agreement Term,
      provided the Customer 

                                      19

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
     replaces this Agreement with another AT&T Carrier Agreement for AT&T Tariff
     F.C.C. Nos. 1 and 2 Services or equivalent services with revenue
     commitments greater than commitments under this Agreement and with a term
     equal or greater than the remaining term of this Agreement.

     6.H.2.  Termination Charge for Discontinuance Prior to End of Agreement
             ---------------------------------------------------------------
     Term.  If the Customer discontinues this Agreement prior to the expiration
     -----                                                                     
     of the Agreement Term, or if AT&T terminates this Agreement or the service
     provided pursuant to this Agreement due to Customer's breach of this
     Agreement, prior to the expiration of the Agreement Term, the Customer will
     be billed for and shall pay within 30 days a Termination Charge.  The
     Termination Charge will be an amount equal to 100% of the waived
     nonrecurring charges provided for in this Agreement at the time of
     discontinuance.  Payment is due within 30 days.

                                      20

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials
<PAGE>
 
                                  SCHEDULE  A
================================================================================

International Usage Rates - AT&T MEGACOM Service-International Calling
-------------------------                                             
Capabilities

1.   Mexico Rate Schedule - This schedule applies to Customer dialed calls to
     stations in Mexico from the U.S. Mainland.

     (a).  The following rates for calls between the U.S. Mainland and the point
     of connection at the international boundary apply for all days of the week
     including holidays.


The rates for Customer Dialed Person (DP), Operator Placed Station (OS) and
Operator Placed Person-to-Person (OP) calls, (as defined in Section 24.1.2.B.
2.(a) of AT&T Tariff F.C.C. No. 27) between the point of connection at the
international boundary and Mexico are as specified in Section 24.1.2.B.2. of
AT&T Tariff F.C.C. No. 27.

The rates for calls between the point of connection at the international
boundary and Mexico are as specified in AT&T F.C.C. Tariff No. 1, Section
3.2.4.L.5, as amended from time to time.


2.   All Other Countries - This schedule applies to Customer dialed calls to
                           stations in All Other Countries from the U.S. 
                           Mainland.

                                      21

                         CONFIDENTIAL AND PROPRIETARY
                                    between
                                 AT&T and BCGI

-------------------                                                -------------
Customer's Initials                                                AT&T Initials