Document:

<PAGE>

                                                                    EXHIBIT 4.13

Strictly Private & Confidential

Dear [Director]:

This letter contains the terms of our offer to you to hold office as a
non-executive director of Cambridge Antibody Technology Group plc [the
"Company"]. As you are aware the Board of Directors of the Company is concerned
that the Combined Code followed as regards the role and duties of non-executive
directors. The terms of the offer are as follows:

(1)    Your appointment will take effect as of [________].

(2)    Your role will be that of an independent director, bringing an
       objectivity and independence of view borne by your outside experience,
       helping the board to provide the Company with effective leadership and
       ensuring the continuing effectiveness of the management team and the high
       standards of probity within the Company.

(3)    The Company will pay you an annual director's fee of [________]/1/,
       payable half-yearly in arrears, on 31 March and 30 September. The board
       reserves the right to pay you an additional fee where the discharge of
       your fiduciary obligations has made exceptional demands on your time.
       Remuneration of non-executive directors will be reviewed periodically by
       the Board.

(4)    In addition to your general fiduciary responsibilities you may be
       required to serve on the Audit Committee and or the Remuneration
       Committee, each of which are committees of the board consisting entirely
       of non-executive directors. The board may also need you to serve on other
       committees and/or to hold additional offices within the group, where best
       practice requirements dictate that a non-executive presence is required.

(5)    You are expected to attend each meeting of the board and of any committee
       to which you are appointed. If you are unavoidably unable to attend,
       prior notice should be given to the Chairman of the board.

___________________________
/1/  The salary of each director is disclosed in the text of the registration
     statement.
<PAGE>

(6)    You will be fully reimbursed for all out-of-pocket expenses necessarily
       incurred by you in discharging your duties (including any legal fees
       incurred by you for obtaining independent legal advice in connection with
       the discharge of your fiduciary responsibilities). The Company's
       procedures require you to obtain authorisation in advance from the board
       for any item of expenditure over (pound)1,000. Any expenses to be
       incurred outside your own country or for international travel will be
       reimbursed at a rate agreed from time to time by the board.

(7)    Because of your non-executive status, you will not be eligible to
       participate in any share option, bonus schemes, pension schemes or other
       benefits of the kind available to executive directors of the Company. The
       Company does, however, maintain directors' and officers' liability
       insurance, details of which are available from the Company Secretary.

(8)    Your appointment will at all times be terminable by six months' prior
       written notice given by either side. Upon the expiry of notice served on
       you to terminate your appointment, you agree to resign from your office
       as a director (and any other offices or appointments you may hold as
       nominee or representative of the Company or any Group Company) and, if
       you should fail to do so within seven days of being so required, the
       Company is hereby irrevocably authorised to appoint some person in your
       name and on your behalf to sign any document or do any thing necessary or
       requisite to effect such resignation(s) (without prejudice to any claims
       you may have against the Company for loss of office).

(9)    Your appointment will terminate automatically without any requirement for
       notice or compensation if you:

       (i)   vacate your office under Article 110 of the Company's Articles of
             Association;

       (ii)  are removed from office as a director by any resolution duly
             proposed and resolved by the shareholders of the Company in general
             meeting (provided always that, where a poll is demanded, the result
             of the poll will count); or

       (iii) are not re-elected as a director when you submit yourself for re-
             election.

(10)   Your fiduciary duties to the Company require you, in particular, at all
       times:

       (i)   to maintain the confidentiality of all information you acquire by
             virtue of your appointment;

       (ii)  to act in good faith in the Company's interests at all times;

       (iii) to act at all times for the proper purposed of the Company;

       (iv)  to carry out your responsibilities with the care, skill and
             diligence that the Company is reasonably entitled to expect from
             someone of your experience
<PAGE>

             and expertise; and

       (v)   to act only with the proper authority of the Company.
<PAGE>

(11)   You must not make any statements on the Company's or any Group Company's
       behalf concerning the Company or any Group Company to the press, media,
       venture capitalists, brokers, banks, financial analysts and/or anyone
       associated with the stock market or investor community unless authorised
       by the board to do so.

(12)   In order that the board can give its approval, it will be necessary for
       you to disclose to the board all outside directorships and other (direct
       or indirect) interests, employments, consultancies or associations held
       by you or members of your family. You must also keep the board informed
       on a continuing basis of all changes to such arrangements. During your
       appointment you will not be free, unless prior written approval has been
       given by the board, to take up new directorships or hold other interests
       in the same industry as the Company or which could give rise to a
       conflict of interest in some other way.

Please sign, date and return the attached copy of this letter to me, confirming
your acceptance of the appointment and its terms. If the terms of this
appointment cause you any difficulty, please let me know.

Yours faithfully

[Company Officer]

I agree to the terms and conditions set out in a letter dated [__________] (of
which a copy is attached) relating to my appointment as a non-executive director
of Cambridge Antibody Technology Group plc.

IN WITNESS WHEREOF I HAVE EXECUTED THIS DOCUMENT AS A DEED ON THE DATE SET OUT
BELOW:

 ..............................
Signed
<PAGE>

In the presence of:

 .......................................
Signed

 .......................................
Name

 .......................................
Address

 .......................................
Date<PAGE>   1
                                                                   EXHIBIT 10.20

                         WORLDCOM NETWORK SERVICES, INC.

                     CLASSIC/TRANSCEND(TM)SWITCHED SERVICES

                            PROGRAM ENROLLMENT TERMS

         These PROGRAM ENROLLMENT TERMS (the "PET") are made by and between
WorldCom Network Services, Inc. ("WORLDCOM") and AmeriVision Communications,
Inc. ("CUSTOMER") and are a part of their Telecommunications Services Agreement
for Switched Services. Capitalized terms not defined herein shall have the
meaning ascribed to them in the TSA, the Service Schedule or the applicable Rate
and Discount Schedule.

1.       SERVICE TERM: The Service Term shall commence as of --**-- (the
         "EFFECTIVE DATE") and shall continue through and include --**-- (the
         "SERVICE TERM"), subject to earlier termination as provided in
         Subsection 2(B) below. Provided, however, notwithstanding the
         immediately preceding sentence, the rates set forth herein will be
         effective as of --**-- (the "RATE EFFECTIVE DATE"). Upon expiration of
         the Service Term, the Switched Services in question will continue to be
         provided pursuant to the same terms and conditions as are then in
         effect (including without limitation, the applicable rates, discounts
         and commitments, if any), subject to termination by either party upon
         sixty (60) days prior written notice to the other party.

2.       CUSTOMER'S MINIMUM REVENUE COMMITMENT:

         (A) Commencing with the Effective Date (as determined under Section 1
         above) and continuing through the end of the Service Term (including
         any extensions thereto) (the "COMMITMENT PERIOD"), Customer agrees to
         maintain, on a take-or-pay basis, cumulative Monthly Revenue (as
         defined in the applicable Rate and Discount Schedule) equal to at least
         the amounts shown below by the end of the respective months listed
         ("CUSTOMER'S MINIMUM REVENUE COMMITMENT").

<TABLE>
<CAPTION>

             END OF           CUSTOMER'S       END OF           CUSTOMER'S
             MONTH            COMMITMENT       MONTH            COMMITMENT
             -----            ----------       -----            ----------
<S>                           <C>              <C>              <C>
               1                $2,000,000       19             $38,000,000
               2                $4,000,000       20             $40,000,000
               3                $6,000,000       21             $42,000,000
               4                $8,000,000       22             $44,000,000
               5               $10,000,000       23             $46,000,000
               6               $12,000,000       24             $48,000,000
               7               $14,000,000       25             $50,000,000
               8               $16,000,000       26             $52,000,000
               9               $18,000,000       27             $54,000,000
              10               $20,000,000       28             $56,000,000
              11               $22,000,000       29             $58,000,000
              12               $24,000,000       30             $60,000,000

</TABLE>

--------------------
         --**-- This symbol signifies information from the agreement that has
been omitted because the Company has requested confidential treatment. The
information has been filed separately with the Securities and Exchange
Commission.

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         (B) Notwithstanding anything to the contrary contained in Subsection
         (A) above, as soon as Customer's cumulative Monthly Revenue (which will
         include any Deficiency Charges actually paid by Customer) is equal to
         at least $72,000,000, either party may cancel this Agreement in its
         entirety upon at least ninety (90) prior written notice to the other
         party.

3.       DEFICIENCY CHARGE: In the event Customer does not maintain Customer's
         Minimum Revenue Commitment in any month during the Commitment Period
         (regardless of whether Customer has commenced using any or all of the
         Switched Services described herein), then for those month(s) only,
         Customer will pay WorldCom the difference between Customer's Minimum
         Revenue Commitment and Customer's actual Monthly Revenue (as described
         in the applicable Rate and Discount Schedule) (the "DEFICIENCY
         CHARGE"). The Deficiency Charge will be due at the same time payment is
         due for Service provided to Customer, or immediately in an amount equal
         to Customer's Minimum Revenue Commitment for the unexpired portion of
         the Service Term, if WorldCom terminates this Agreement based on
         Customer's default. Provided, however, WorldCom agrees to waive any
         Deficiency Charges that arise solely due to a catastrophic network
         event which materially prevents Customer's use of Services hereunder
         sufficient to satisfy Customer's Minimum Revenue Commitment. In such
         case, Customer shall have the burden of proof in establishing the date
         and duration of such event as well as the general sources of Customer's
         traffic affected by such event. Provided, for purposes of this
         Agreement, any catastrophic network events lasting less than --**--
         and/or affecting less than --**-- minutes of Customer's traffic will be
         deemed not material.

4.       CANCELLATION WITHOUT CHARGE: The parties agree to substitute Subsection
         2(C) of the TSA to read in its entirety as follows:

         (C) Cancellation Without Charge. Notwithstanding anything to the
         contrary contained in Subsection 2(A) above, Customer may cancel this
         Agreement without incurring any cancellation charge if:

                  i. WorldCom fails to provide a network as warranted in Section
                  8 below and fails to cure such default within five (5) days
                  following written notice from Customer; or

                  ii. WorldCom fails to (a) deliver call detail records promptly
                  based on the frequency selected by Customer (i.e., monthly,
                  weekly or daily); or (b) submit ANI(s) relevant to such
                  Service Requests to the LECs within the time period described
                  in Subsection 1(B) above. Provided, however, Customer must
                  give WorldCom written notice of any such default under this
                  Subpart (ii) and an opportunity to cure such default within
                  five (5) days of the notice. In the event WorldCom fails to
                  cure any such default within the five-day period set forth in
                  this Subpart (ii) on more than three (3) occasions within any
                  six (6) month period, Customer may cancel this Agreement
                  without incurring any cancellation charge.

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5.       DISPUTED TRANSFER CHARGES: The parties agree to substitute the first
         sentence only of Subsection 3(A) and Subsection 3(B) of the TSA to read
         in their entirety as follows:

         (A) End Users. Customer will use reasonable efforts to obtain and upon
         WorldCom's request will provide WorldCom (within two (2) business days
         of the date of the request) a written Letter of Agency ("LOA")
         acceptable to WorldCom [or with any other means if approved by the
         Federal Communications Commission ("FCC") and any applicable public
         utility commission ("PUC") and accepted by the applicable local
         exchange provider provided the local exchange provider has the
         authority to accept or deny certain forms of LOAs (provided, further,
         nothing contained herein will require WorldCom to challenge the right
         of local exchange providers to accept or deny certain forms of LOAs),
         for each ANI indicating the consent of such end user of Customer ("END
         USER") to be served by Customer and transferred (by way of such End
         User's designated PIC) to the WorldCom network prior to order
         processing.

         (B) Transfer Charges/Disputed Transfers. Customer agrees that it is
         responsible for (i) all charges incurred by WorldCom to change the PIC
         of End Users to the WorldCom network, (ii) all charges incurred by
         WorldCom to change End Users back to their previous PIC arising from
         disputed transfers to the WorldCom network plus, at WorldCom's option,
         an administrative charge equal to --**-- of such charges, and (iii) any
         other damages suffered by or awards against WorldCom resulting from
         disputed transfers unless such damages or awards are the result of
         actions taken solely by WorldCom without any involvement (either
         directly or indirectly) by Customer.

6.       PAYMENT TERMS: The parties agree to substitute Subsection 5(A) and 5(B)
         of the TSA to read in their entirety as follows:

         (A) Payment. WorldCom billings for Switched Services hereunder are made
         on a monthly basis (or such other basis as may be mutually agreed to by
         the parties) following Start of Service. Subject to Subsection 5(C)
         below, Switched Services shall be billed at the rates set forth in the
         applicable Rate and Discount Schedule attached hereto. Customer will be
         notified of WorldCom's time of day rate periods (including WorldCom
         Recognized National Holidays). Discounts, if any, applicable to the
         rates for certain Services are set forth in the Rate and Discount
         Schedule. Customer will pay all undisputed charges relative to each
         WorldCom invoice for Switched Services within (i) --**-- days of the
         invoice date set forth on each WorldCom invoice to Customer with
         respect to Services provided in months 1 through 3 following the
         Effective Date of this Agreement, (ii) --**-- days of the invoice date
         set forth on each WorldCom invoice to Customer with respect to Services
         provided in months 4 through 6 following the Effective Date of this
         Agreement, and (iii) --**-- days of the invoice date set forth on each
         WorldCom invoice to Customer with respect to Services provided through
         the remainder of the Service Term (collectively, the "DUE DATE"). If
         payment is not received by WorldCom on or before the Due Date, Customer
         shall also pay a late fee in the amount of the lesser of one and
         one-half percent (1 1/2%) of the unpaid

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         balance of the charges for Switched Services rendered per month or the
         maximum lawful rate under applicable state law. Commencing with the
         Effective Date and continuing through the end of the Service Term,
         Customer agrees to provide WorldCom (a) unaudited financial statements
         within --**-- days following each month, (b) "reviewed" financial
         statements within --**-- days following each quarter, and (c) audited
         financial statements within --**-- days following the end of each of
         Customer's fiscal years.

         (B) Taxes. Customer acknowledges and understands that WorldCom computes
         all charges herein exclusive of any applicable federal, state or local
         use, excise, gross receipts, sales and privilege taxes, duties, fees or
         similar liabilities (other than general income or property taxes),
         whether charged to or against WorldCom or customer because of the
         Switched Services furnished to Customer ("ADDITIONAL CHARGES").
         Customer shall pay such Additional Charges in addition to all other
         charges provided for herein. Customer will not be liable for certain
         Additional Charges if Customer provides WorldCom with an appropriate
         exemption certificate. Provided, to the extent Customer is not an "end
         user" of the Services provided hereunder, with respect to any
         Additional Charges which are assessed solely on WorldCom's end users
         ("END USER CHARGES"), WorldCom agrees not to assess Customer such End
         User Charges. Provided, however, in the event WorldCom is required to
         collect End User Charges from Customer, Customer agrees to pay WorldCom
         such End User Charges unless Customer provides WorldCom a written
         certification, signed by an officer of Customer, that Customer has
         directly paid such End User Charges.

7.       PAYMENT OF DISPUTED AMOUNTS: Notwithstanding anything to the contrary
         contained in Subsection 5(D) of the TSA, in the event Customer pays
         WorldCom any amount which is ultimately determined not to be due
         WorldCom, WorldCom agrees to pay Customer such amount plus interest on
         such amount equal to one and one-half (1 1/2%) of such amount per month
         or the maximum lawful rate under applicable state law.

8.       CREDIT: The parties agree to delete the first two sentences of
         Subsection 6(A) of the TSA.

9.       REMEDIES FOR BREACH: In the event WorldCom elects its remedies under
         Subsection 7(B) of the Agreement and bills Customer's End Users
         directly, WorldCom agrees to collect any amounts owing from such End
         Users in good faith and in accordance with reasonable business
         practices. In the event WorldCom collects any amounts from Customer's
         End Users, such amounts will offset any amounts owed by Customer under
         this Agreement. In other words, Customer's liability for charges for
         Services rendered and the Deficiency Charge, if applicable, will be
         reduced by any amounts WorldCom collects from Customer's End Users.

10.      FORCE MAJEURE: The parties agree to substitute Section 10 of the TSA to
         read in its entirety as follows:

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         If either party's performance of this Agreement or any obligation
         hereunder (excluding payments owed by Customer for Services rendered by
         WorldCom) is prevented, restricted or interfered with by causes beyond
         its reasonable control including, but not limited to, acts of God,
         fire, explosion, vandalism, cable cut, storm or other similar
         occurrence, any law, order, regulation, direction, action or request of
         the United States government, or state or local governments, or of any
         department, agency, commission, court bureau, corporation or other
         instrumentality of any one or more such governments, or of any civil or
         military authority, or by national emergency, insurrection, riot, war,
         strike, lockout or work stoppage or other labor difficulties, or
         supplier failure, shortage, breach or delay, then the affected party
         shall be excused from such performance on a day-to-day basis to the
         extent of such restriction or interference. The affected party shall
         use reasonable efforts under the circumstances to avoid or remove such
         causes or nonperformance and shall proceed to perform with reasonable
         dispatch whenever such causes are removed or cease.

11.      OTHER AGREEMENTS: The parties agree to substitute Subsection 24(B) of
         the TSA to read in its entirety as follows:

         (B) Third Party Agreements. If Customer acquires or merges or combines
         with a third party after the Effective Date of this Agreement, and such
         third party has existing agreement(s) with a member of the WorldCom
         Group (collectively referred to as the "THIRD PARTY AGREEMENTS") for
         the provision of switched telecommunications services ("THIRD PARTY
         EXISTING SERVICES"), then ninety (90) days following the date of such
         acquisition, merger or combination (or such earlier date contained in a
         written notice from customer to WorldCom) (the "TRANSFER DATE"), if
         requested by WorldCom, Customer agrees to select one Agreement (either
         this Agreement or a Third Party Agreement) (the "SURVIVING AGREEMENT")
         pursuant to which all switched services will be provided to Customer
         and all members of the Customer Group and all other agreements (the
         "CANCELED AGREEMENTS") will be canceled and no longer in force or
         effect except for commitments, if any, contained in the Canceled
         Agreements and charges and credits due for Services provided prior to
         the effective date of cancellation of such Canceled Agreements.
         Further, as of the effective date of cancellation, Third Party Existing
         Services or, if applicable, the Services provided under this Agreement
         will be provisioned under the Surviving Agreement, and the aggregate
         commitment(s) (e.g., revenue, volume, minute, etc.) remaining under the
         Canceled Agreements shall be added on a pro rata basis to the
         commitment(s), if any, existing under the Surviving Agreement.
         Simultaneous with the closing of such acquisition, combination or
         merger, Customer will cause such third party and all of its affiliates
         who are parties to such Third Party Agreements, to agree to such
         cancellation(s) as appropriate and the provision of such Services, as
         appropriate under the terms and conditions of the Surviving Agreement
         and Customer agrees to provide WorldCom with reasonable documentation
         evidencing such agreement.

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12.      TARIFF REFERENCES: Except to the extent specifically referenced in this
         Agreement, this Agreement does not incorporate any terms or conditions
         contained in any federal and/or state tariffs filed or to be filed by
         WorldCom or any of its affiliates.

13.      DISPUTE RESOLUTION: If the parties are unable to resolve any dispute
         arising under or relating to this Agreement, the parties may resolve
         such disagreement or dispute as follows:

         (a) Either party may, by written notice to the other party (the
         "DISPUTE NOTICE"), request that a designated representative from each
         of the parties attempt to resolve the matter. Within fifteen (15) days
         after delivery of the Dispute Notice such representatives of both
         parties will use good faith efforts to schedule a meeting at a mutually
         acceptable time and place to attempt to resolve the dispute.

         (b) If the matter has not been resolved within thirty (30) days after
         delivery of the Dispute Notice, or if such representatives fail to meet
         within fifteen (15) days after delivery of such Dispute Notice, either
         party may initiate mediation in accordance with the procedures set
         forth in (C) below. All negotiations conducted by such representatives
         shall be confidential and shall be treated as compromise and settlement
         negotiations for purposes of federal and state rules of evidence.

         (c) If such representatives are unable to resolve the dispute or have
         failed to meet, the parties may elect to participate in a nonbinding
         mediation procedure as follows:

                  (A) A mediator will be selected by having counsel for each
                  party agree on a single person to act as mediator. The
                  parties' counsel as well as up to three (3) representatives of
                  each of the parties will appear before the mediator at a time
                  and place determined by the mediator, but not more than sixty
                  (60) days after delivery of the Dispute Notice. The fees of
                  the mediator and other costs of the mediation will be shared
                  equally by the parties.

                  (B) Each party will present a review of the matter and its
                  position with respect to such matter. At the conclusion of
                  both presentations the parties may ask questions of each
                  other. Either party may abandon the mediation procedure at the
                  end of the presentation and question periods and the mediation
                  procedure shall not be binding on either party.

                  (C) If the matter is not resolved after applying the mediation
                  procedure set forth above, or if either party refuses to take
                  part in the mediation process, either party may initiate legal
                  proceedings to resolve their dispute.

         (D) The provisions of this Section 13 shall not preclude a party form
         instituting legal proceedings seeking injunctive relief (including,
         without limitation, a temporary restraining

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         order) prior to the commencement or completion of the specified dispute
         resolution procedures.

14.      REQUIREMENTS AGREEMENT: In consideration of the rates set forth in the
         Rate Schedule, and other good and valuable consideration, the receipt
         and sufficiency of which are hereby acknowledged, during the Service
         Term Customer agrees to purchase one hundred percent (100%) of its
         telecommunications services requirements for SWITCHED ACCESS Service
         (1+ and Toll Free) (which services are described in this Agreement)
         from WorldCom under the terms and conditions set forth in this
         Agreement ("CUSTOMER'S REQUIREMENTS OBLIGATION"). Upon request from
         WorldCom, Customer agrees to provide WorldCom reasonable documentation
         evidencing Customer's compliance with this Section 14 and if requested
         by WorldCom, agrees to allow WorldCom or its representatives to audit
         Customer's books and records as may be necessary solely to ensure
         Customer's compliance with Customer's Requirements Obligation. In the
         event Customer is in breach of this Agreement, in addition to
         WorldCom's other rights and remedies described in this Agreement,
         notwithstanding anything to the contrary contained in the Agreement,
         WorldCom shall have the right to immediately increase Customer's
         SWITCHED ACCESS Service rates set forth in the Rate Schedule to --**--.
         Any increase as described herein will not affect Customer's Minimum
         Revenue Commitment set forth in Section 2 above.

15.      SEMI-ANNUAL REVIEW OF RATES: Provided Customer is in substantial
         compliance with the terms of this Agreement, commencing September 1,
         1999, and continuing on the first day of every seventh (7th) month
         thereafter (i.e., March 1, 2000; September 1, 2000; March 1, 2001;
         etc.), WorldCom and Customer agree to review the rates hereunder with a
         view to adjusting in good faith such rates taking into account (i)
         rates then generally available to WorldCom's other wholesale customers
         under other "programs" being offered by WorldCom when taken as a whole,
         and (ii) rates then generally available to WorldCom's other wholesale
         customers for similar services, commitments and other terms. In
         conducting such review, the parties agree to take into account state
         and/or federal mandates regarding local access reform, if any, that may
         affect the cost of the Services provided hereunder and which result in
         either an increase or decrease to such rates. Provided, however,
         nothing contained in this Section 15 will obligate WorldCom to reduce
         Customer's rates under this Agreement.

16.      CUSTOMER PROPRIETARY INFORMATION: In addition to WorldCom's obligations
         to protect Customer's Confidential Information under Section 20 of the
         TSA, WorldCom agrees to comply with all applicable laws, rules and
         regulations regarding Customer's proprietary network information and
         the proprietary network information of Customer's End Users which
         information has been directly provided or disclosed by Customer to
         WorldCom.

17.      SUBORDINATION AGREEMENT: Simultaneous with the execution of this
         Agreement, WorldCom agrees to execute the attached Intercreditor
         Agreement by and between WorldCom, Customer and Coast Business Credit,
         a division of Southern Pacific Bank.

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18.      CREDIT/SETTLEMENT:

         (A) In consideration of the terms and conditions contained in this
         Agreement, Customer's payment to WorldCom of --**-- on or before the
         due date of WorldCom's April 1, 1999 invoice, and other good and
         valuable consideration the receipt and sufficiency of which are hereby
         acknowledged, upon execution of this Agreement, WorldCom agrees to give
         Customer a credit (the "CREDIT") equal to --**-- which the parties
         agree equals all invoiced and unpaid charges including interest and
         late fees owed by Customer for Services provided by WorldCom prior to
         January 1, 1999 (i.e., up through and including the January, 1999
         invoice) (the "SETTLEMENT DATE") (including any Services provided to
         Hebron Communication Corporation or American Electronics Corporation
         d/b/a Discount Long Distance assertedly through Customer by WorldCom
         through the Settlement Date. For purposes of this Agreement, such
         Services shall include without limitation (i) the following WorldCom
         billing account numbers for Switched Services: --**--; and the
         following WorldCom billing account numbers for private line services:
         --**--, and any other accounts for which Customer had payment
         responsibility under that certain Payment Agreement dated June 1, 1996,
         and executed by Customer, WorldCom and National Telephone &
         Communications, Inc., including without limitation, billing account
         numbers --**--. In addition to the Credit described herein, WorldCom
         agrees to waive any finance charges up through and including March 31,
         1999 (i.e., the April, 1999 invoice). WorldCom acknowledges that the
         rates charged to Customer from and after November 30, 1998, through the
         Rate Effective Date described in Section 1 above shall be consistent
         with the rates provided under the WilMAX Telecommunications Services
         Agreement dated June 1, 1996 (the "NTC AGREEMENT"), as referenced in
         that certain Payment Agreement by and between WorldCom, Customer and
         National Telephone & Communications, Inc. dated June 1, 1996.

         (B) In consideration hereof, Customer and WorldCom, together with and
         on behalf of their respective predecessors, successors, parents,
         subsidiaries, affiliates, assigns, agents, directors, officers,
         employees and shareholders hereby release the other party and its
         respective predecessors, successors, parents, subsidiaries, affiliates,
         assigns, agents, directors, officers, employees and shareholders, from
         any and all claims, demands, damages, causes of action, debts,
         obligations, liabilities or controversies of any kind whatsoever,
         whether at law or in equity, whether before a local, state or federal
         court, arbitrator or state or federal administrative agency or
         commission, and whether known or unknown, liquidated or unliquidated,
         that the releasing party has or may have against the other on account
         of or in any way related to the NTC Agreement, any Services provided or
         billed to Customer prior to the Settlement Date, or any statements
         and/or representations made by the other party's personnel regarding
         the Services provided to Customer (the "DISPUTED MATTERS"). Upon
         receipt of the Credit, (i) it shall be the full and final settlement of
         each party's disputes and claims pertaining to the Disputed Matters,
         and (ii) each party shall thereafter be barred from bringing any
         charge, complaint or other action against the other relating to the
         Disputed Matters for all periods prior to the Settlement Date. It is
         understood and agreed by the parties that this Amendment is not to be
         construed or used as an admission of any liability

4/15/99                            Page 8 of 9

                          CONFIDENTIAL - EXECUTION COPY

<PAGE>   9

         whatsoever by either party, its officers, directors, employees, agents,
         representatives, affiliates or subsidiaries, which liability is
         expressly denied, nor is it to be construed or used as an admission
         that a party has committed or engaged in any deceptive or unlawful act,
         violation or other breach of duty imposed by the NTC Agreement,
         applicable tariffs or applicable law.

4/15/99                            Page 9 of 9

                          CONFIDENTIAL - EXECUTION COPY

<PAGE>   10

         IN WITNESS WHEREOF, the parties have executed these
Classic/TRANSCEND(TM) Switched Services Program Enrollment Terms.

WORLDCOM NETWORK SERVICES, INC.                 AMERIVISION COMMUNICATIONS,
INC.

By:     /s/ John H. Krummez                     By:  /s/ Stephen D. Halliday
   -------------------------------                 -----------------------------
       (Signature)                                         (Signature)

           John H. Krummez                              Stephen D. Halliday
----------------------------------              --------------------------------
             (Print Name)                                  (Print Name)

         Senior Vice President                               President
----------------------------------              --------------------------------
               (Title)                                       (Title)

4/15/99                           Page 10 of 9

                          CONFIDENTIAL - EXECUTION COPY

<PAGE>   11

                         WORLDCOM NETWORK SERVICES, INC.

                                SWITCHED SERVICES

                         RATE SCHEDULES FOR AMERIVISION

         Capitalized terms not defined in this Rate Schedule shall have the
meaning ascribed to them in the Telecommunications Services Agreement,
TSA#AVI-990301, between AmeriVision Communications, Inc. and WorldCom Network
Services, Inc.

                                      RATES

(A)      TERMINATION Service

         --**--

(B)      TOLL FREE ORIGINATION Service

         --**--

(C)      SWITCHED ACCESS Service

         --**--

(D)      DEDICATED ACCESS Service

         --**--

(E)      TRAVEL CARD Service

         --**--

(F)      Directory Assistance

         --**--

ATTACHMENTS:

         --**--

-------------------
         --**-- This symbol signifies information from the agreement that has
been omitted because the Company has requested confidential treatment. The
information has been filed separately with the Securities and Exchange
Commission.

<PAGE>   12
                                                                  Exhibit 10.21

                               SECURITY AGREEMENT

         AMERIVISION COMMUNICATIONS, INC., an Oklahoma corporation with its
principal office at 5900 Mosteller Drive, Suite 1850, Oklahoma City, Oklahoma
73112 ("DEBTOR"), and WORLDCOM NETWORK SERVICES, INC., a Delaware corporation,
with its principal office at 6929 North Lakewood Avenue, Tulsa, Oklahoma 74117
("SECURITY PARTY"), agree as follows:

         SECTION 1.  CREATION OF SECURITY INTEREST

         Debtor hereby grants to secured Party a security interest in the
property described in Section 2 of this Agreement (the "COLLATERAL") to secure
performance and payment of (i) all obligations arising under or in connection
with that certain Telecommunications Services Agreement dated April 20, 1999
and more particularly described as TSA#AVI-990301 (including those certain
Program Enrollment Terms attached thereto) (collectively, the "TSA") between
Debtor and Secured Party, and all related instruments, documents or agreements
and any amendments, extensions, renewals or replacements of or to the
foregoing; and (ii) all other obligations and indebtedness of Debtor to Secured
Party of whatever kind and however created whether presently existing or
hereafter arising. All of the foregoing obligations and indebtedness described
in this Section 1 shall hereinafter be referred to as the "SECURED
INDEBTEDNESS," and the TSA and all other documents evidencing or giving rise to
the Secured Indebtedness shall hereinafter be referred to collectively as the
"SECURITY INSTRUMENTS."

         SECTION  2.  COLLATERAL

         (a) As collateral for the Secured Indebtedness, Debtor hereby assigns
and grants to Secured Party a lien and security interest in all of the Debtor's
following property, wherever located, and whether now owned or hereafter
acquired or created:

         (b) All of Debtor's now owned and hereafter acquired accounts (whether
or not earned by performance), letters of credit, contract rights, chattel
paper, instruments, securities, documents, securities accounts, security
entitlements, commodity contracts, commodity accounts, investment property and
all other forms of obligations at any time owing to Debtor, all guaranties and
other security therefor, all merchandise returned to or repossessed by Debtor,
and all rights of stoppage in transit and all other rights or remedies of any
unpaid vendor, lienor or secured party (collectively, "RECEIVABLES").

         (c) All general intangibles of Debtor, whether now owned or hereafter
created or acquired by Debtor, including, without limitation, all choses in
action, causes of action, corporate or other business records, deposit
accounts, investment property (as such term is defined in the Uniform
Commercial Code in effect in the state of Oklahoma), inventions, designs,
drawings, blueprints, patents, patent applications, trademarks and the goodwill
of the business symbolized thereby, names,

                                  Page 1 of 9

<PAGE>   13

trade names, trade secrets, goodwill, copyrights, registrations, licenses,
franchises, customer lists, all documents containing the names, addresses,
telephone numbers, and other information regarding Debtor's customers and
tapes, programs, printouts, disks, and other material and documents relating to
the recording, billing or analyzing of any of the foregoing, customer contracts
for the furnishing by Debtor of telecommunications services, and billing and
collection contracts, whether evidenced by a document or otherwise, security
and other deposits, rights in all litigation presently or hereafter pending for
any good cause or claim (whether in contract, tort or otherwise), and all
judgments now or hereafter arising therefrom, all claims of Debtor against
Secured Party, rights to purchase or sell real or personal property, rights as
a licensor or licensee of any kind, royalties, telephone numbers, proprietary
information, purchase orders, and all insurance policies and claims (including
without limitation life insurance, key man insurance, credit insurance,
liability insurance, property insurance and other insurance), tax refunds and
claims, computer programs, discs, tape and tape files, claims under guaranties,
security interests or other security held by or granted to Debtor, all rights
to indemnification and all other intangible property of every kind or nature
(other than Receivables).

         (d) All of Debtor's now owned and hereafter acquired goods,
merchandise or other personal property, wherever located, to be furnished under
any contract of service or held for sale or lease (including without limitation
all raw materials, work in process, finished goods and goods in transit, and
including without limitation all farm products), and all materials and supplies
of every kind, nature and description which are or might be used or consumed in
Debtor's business or used in connection with the manufacture, packing,
shipping, advertising, selling or finishing of such goods, merchandise or other
personal property, and all warehouse receipts, documents of title and other
documents representing any of the foregoing (collectively, "INVENTORY").

         (e) All of Debtor's present and hereafter acquired machinery, molds,
machine tools, motors, furniture, equipment, furnishings, fixtures, trade
fixtures, motor vehicles, tools, parts, dies, jigs, goods and other goods
(other than Inventory) of every kind and description used in Debtor's
operations or owned by Debtor and any interests in any of the foregoing and all
attachments, accessories, accessions, replacements, substitutions, additions or
improvements to any of the foregoing, wherever located.

         (f) All proceeds of any of the foregoing, all products of any of the
foregoing, and all books, records and documents relating to any and all of the
foregoing, whether in the form of writing, microfilm, microfiche, tape, or
electronic media.

         SECTION 3.  DEBTOR'S REPRESENTATIONS AND WARRANTIES

         Debtor hereby represents and warrants to Secured Party that Debtor is
and will at all times in the future be, the sole owner of the Collateral,
having good and marketable title thereto (except for items of Equipment which
are leased by Debtor), free and clear of any and all liens, charges, security
interests, encumbrances, adverse claims or rights of others created by any acts
or omissions of Debtor, except for the security interest granted to Secured
Party and any and all liens and security interests that are defined as
Permitted Liens in that certain Loan and Security Agreement between Debtor and
Coast Business Credit ("COAST") dated February 4, 1999, as the same may be
amended from time to time, including, but not limited to the present and future
liens and security interests in favor of Coast and any and all additional
security interests and liens consented to in writing by Coast

                                  Page 2 of 9

<PAGE>   14

(collectively, "PERMITTED LIENS"). Debtor will at all times defend Secured
Party and the Collateral against all claims of others other than the holders of
Permitted Liens. None of the Collateral is or will be affixed to any real
property in such a manner, or with such intent, as to become a fixture. Debtor
is not and will not become a lessee under any real property lease pursuant to
which the lessor may obtain any rights in any of the Collateral and no such
lease now prohibits, restrains, impairs or will prohibit, restrain or impair
Debtor's right to remove any Collateral from the leased premises. Whenever any
Collateral is located upon premises in which any third party has an interest
(whether as owner, mortgagee, beneficiary under a deed of trust, lien or
otherwise), Debtor shall, whenever requested by Secured Party, use its
reasonable best efforts to cause such third party to execute and deliver to
Secured Party, in form acceptable to Secured Party, such waivers and
subordinations as Secured Party shall specify, so as to ensure that the rights
of the Secured Party in the Collateral are, and will continue to be, superior
to the rights of any such third party. Debtor will keep in full force and
effect, and will comply with all the terms of, any lease for a Leased Location
where any of the Collateral now or in the future may be located.

         SECTION 4.  EVENTS OF DEFAULT

         The following events are "EVENTS OF DEFAULT":

         4.1 Failure to Pay. Debtor does not pay when due any amount due under
any of the Security Instruments or the Debtor otherwise breaches the provisions
thereof, and such nonpayment or other breach is not cured within any cure
period provided thereunder.

         4.2 Limitations Regarding Collateral. The Debtor sells, transfers,
leases or otherwise disposes of any of the Collateral, or attempts, offers or
contracts to do so (other than in the ordinary course of Debtor's business), or
Debtor creates, permits or suffers to exist any lien, security interest,
encumbrance, claim or right in or to the Collateral other than Permitted Liens
and those in favor of Secured Party (the "OTHER ENCUMBRANCES"). Debtor will, at
Debtor's sole expense, defend the Collateral against and take such other action
as is necessary to remove such Other Encumbrances and defend the right, title
and interest of Secured Party in and to any of Debtor's rights to the
Collateral, including without limitation any proceeds and products thereof,
against the claims and demands of all persons other than the holder of
Permitted Liens.

         4.3 Misrepresentation. Any representation or warranty made by the
Debtor herein or in any of the Security Instruments proves to have been untrue
in any material respect, or any representation, statement (including Financial
Statements), certificate or data furnished or made by the Debtor (or any
officer, accountant or attorney of the Debtor) hereunder or under any of the
Security Instruments proves to have been untrue in any material respect, as of
the date as of which the facts therein set forth were stated or certified.

         4.4 Impairment of Collateral. Secured Party, in good faith, considers
any Collateral to be unsafe or in such danger of misuse that Secured Party's
prospect of or right to payment or performance under this Agreement or any
instrument or agreement required hereunder or under any other agreement between
Secured Party and Debtor is materially impaired.

                                  Page 3 of 9

<PAGE>   15

         4.5 Cross Default. Debtor breaches, defaults, or commits an event of
default under any other agreement, document or instrument between Secured Party
(or an affiliate of Secured Party) and Debtor and such breach, default or event
of default is not cured within any cure period provided thereunder.

         4.6 Change of Name or Principal Place of Business. Debtor changes its
name, or its principal place of business, or changes its corporate structure in
any way that would make filed financing statements misleading without giving
Secured Party at least thirty (30) days advance written notice of such change
or move, and ensuring that any steps necessary to continue the perfection and
priority of Secured Party's security interest in the Collateral shall have been
taken, all at Debtor's expense.

         4.7 Opportunity to Cure. Any Event of Default described in Subsections
4.1, 4.2 and 4.3, 4.4 and 4.5 may be cured within five (5) calendar days after
written notice by Secured Party to Debtor.

         SECTION 5.  SECURED PARTY'S RIGHTS

         5.1 Rights of Secured Party Upon Default. If there is an Event of
Default and such default is not cured within any applicable cure period, the
Secured Party may, at its option and at any time thereafter:

                  (a) Declare the entire aggregate amount of the Secured
                  Indebtedness then outstanding and the interest and other fees
                  and expenses accrued thereon, and all other obligations of
                  debtor to Secured Party to be immediately due and payable
                  without notice and without presentment, demand, protest,
                  notice of protest, or other notice of default or dishonor of
                  any kind, all of which are hereby expressly waived by the
                  Debtor;

                  (b) require Debtor to assemble the Collateral, including any
                  books and records pertaining to the Collateral, and make them
                  available to Secured Party at a place designated by Secured
                  Party;

                  (c) notify any account debtor, any buyers of the Collateral,
                  and any other person of Secured Party's interest in the
                  Collateral;

                  (d) request confirmation from any account debtor of the
                  status of the account upon which the account debtor is
                  obligated;

                  (e) require Debtor to obtain Secured Party's prior written
                  consent to any sale, agreement to sell, or other disposition
                  of any Collateral (other than in the ordinary course of
                  Debtor's business);

                  (f) remedy any default or waive any default without waiving
                  the default remedies and without waiving any other prior or
                  subsequent default; and

                                  Page 4 of 9

<PAGE>   16

                  (g) take such measures as Secured Party may deem necessary or
                  advisable to take possession of, hold, preserve, process,
                  assemble, insure, collect on, prepare for sale or lease,
                  market for sale or lease, sell or lease, or otherwise dispose
                  of any Collateral.

         Debtor hereby constitutes and appoints Secured Party as Debtor's
attorney-in-fact to perform all acts and execute all documents solely in
connection with the remedies described in this Agreement. This power of
attorney is coupled with an interest and shall be irrevocable until such time
as all of Debtor's obligations under the Security Instruments (including
without limitation, the TSA) are satisfied in full. Secured Party's rights
under this Subsection 5.1 may only be exercised to the extent any amount of the
Secured Indebtedness remains unpaid and specifically may not be exercised with
respect to any amounts in excess of the Secured Indebtedness.

         5.2 Further Documentation; Pledge of Instruments. If Secured Party
reasonably determines that further action is necessary and desirable in order
to obtain the full benefits of this Agreement and the rights and powers granted
herein, Secured Party may request in writing that Debtor execute, deliver and
record further documents, instruments, agreements and amendments (including
without limitation, any financing statements or amendments under the applicable
Uniform Commercial Code), in which case Debtor agrees to act promptly. At any
time and from time to time, upon the written request of Secured Party, Debtor
promptly and duly shall execute, deliver and record any documents, instruments,
agreements and amendments, and take all such further action as Secured Party
may reasonably deem necessary and desirable in obtaining the full benefits of
this Agreement and of the rights and powers herein granted, including, without
limitation, the filing of any financing statements or amendments under the
applicable Uniform Commercial Code. Debtor also hereby authorizes Secured Party
to file any such financing statement or amendment thereto, without the
signature of Debtor, or with a copy or telecopy of Debtor's signature, to the
extent permitted by applicable law, or to execute any financing statement or
amendment thereof on behalf of Debtor as Debtor's attorney-in-fact.

         5.3 Rights Under Uniform Commercial Code. Without limiting any of
Secured Party's rights and remedies under this Agreement, Secured Party may
enforce the security interests and other liens given hereunder, and under all
Security Instruments and documents referred to herein or contemplated hereby,
pursuant to the applicable Uniform Commercial Code and any other applicable law
including all legal and equitable remedies available to lenders generally.

         5.4 Payments of Taxes and Insurance. If Debtor fails to pay any taxes,
assessments, insurance premiums, or other amounts due to third parties as
required by Debtor on the Collateral, Secured Party may in its discretion, upon
reasonable prior notice to Debtor make any such payment reasonably determined
by Secured Party to be due and owing. Any payments made by Secured Party under
this Subsection 5.4 shall not constitute (i) an agreement by Secured Party to
make similar payments in the future, or (ii) a waiver by Secured Party of any
Event of Default under this Agreement. Secured Party need not inquire as to, or
contest the validity of, any such expenses, tax security interest, encumbrance
or lien, and the receipt of the notice for the payment thereof shall be
conclusive evidence that the same was validly due and owing. Debtor agrees to
pay Secured Party, on demand, each payment made by Secured Party under this
Subsection 5.4 together with a late fee, if any, provided in the TSA.

                                  Page 5 of 9

<PAGE>   17

         5.5 Rights and Remedies are Cumulative. All rights and remedies
provided herein are cumulative and may be exercised singly or concurrently, and
are not exclusive of any rights or remedies otherwise provided by law. Any
single or partial exercise of any right or remedy shall not preclude the
further exercise thereof or the exercise of any other right or remedy.

         5.6 Self-Help Remedies. SECURED PARTY MAY ENFORCE ITS RIGHTS UNDER
THIS AGREEMENT WITHOUT RESORT TO PRIOR JUDICIAL PROCESS OR JUDICIAL HEARING.
NOTHING IN THIS AGREEMENT IS INTENDED TO PREVENT DEBTOR OR SECURED PARTY FROM
RESORTING TO JUDICIAL PROCESS AT SUCH PARTY'S OPTION.

         5.7 Sale or Disposition of Collateral. Without limiting the generality
of the foregoing, if there is an Event of Default which the Debtor fails to
cure within any applicable cure period, the Secured Party may, at its option
and at any time thereafter, without further demand of performance, or other
demand, advertisement or notice of any kind (except the notice specified below
of time and place and public or private sale) to or upon Debtor or any other
person (all and each of which demands, advertisements and/or notices are hereby
expressly waived), may forthwith collect, receive, appropriate and realize upon
the Collateral, or any part thereof, in one or more parcel at public or private
sale or sales, at any exchange, broker's board or at any of Secured Party's
offices or elsewhere at such prices as it may deem best, for cash or on credit
or for future delivery without assumption of any credit risk. Secured Party
shall have the right upon any such public sale or sales, and, to the extent
permitted by law, upon any such private sale or sales, to purchase the whole or
any part of said Collateral so sold, free of any right or equity of redemption
in Debtor. To the extent permitted by applicable law, Debtor waives all claims,
damages, and demands against Secured Party arising out of the lawful
repossession, retention or sale of the Collateral in accordance with the terms
hereof.

         5.8 Notice of Sale. Debtor agrees that Secured Party need not give
more than ten (10) days' notice of the time and place of any public sale or of
the time after which a private sale may take place and that such notice is
reasonable notification of such matters.

         5.9 Application of Sale Proceeds. Secured Party shall apply the net
proceeds of any such collection, recovery, receipt, appropriation, realization
or sale, after deducting all reasonable costs and expenses of every kind
incurred therein or incidental to the care, safekeeping or otherwise of any or
all of the Collateral or in any way relating to the rights of Secured Party
hereunder, including reasonable attorneys' fees and legal expenses, to the
payment in whole or in part of the Secured Indebtedness, in such order as
Secured Party may elect. Debtor shall remain liable for any deficiency
remaining unpaid after such application and the reasonable fees of any
attorneys employed by Secured Party to collect such deficiency, and only after
so applying such net proceeds and after the payment by Secured Party of any
other amount required by any provision of law, including Section 9-504(1) of
the Uniform Commercial Code, need Secured Party account for the surplus, if
any, to Debtor.

         5.10 Inspection of Records. Secured Party and any of its employees and
agents may enter upon Debtor's premises at any reasonable time to inspect
Debtor's books and records pertaining to the Collateral.

                                  Page 6 of 9

<PAGE>   18

         5.11 No Consequential Damages. SECURED PARTY SHALL NOT BE LIABLE FOR
ANY CONSEQUENTIAL, SPECIAL, INDIRECT OR INCIDENTAL DAMAGES IN CONNECTION WITH
THIS AGREEMENT OR THE COLLATERAL.

         SECTION 6.  ADDITIONAL PROVISIONS

         6.1 Notices. Any communications between the parties hereto to be given
in writing shall be given by mailing the same, postage prepaid, or by telex,
cable, facsimile, overnight courier, or personal delivery, to each party at
their addresses set forth below or to such other addresses as either party may
in writing hereafter indicate. Any communication shall be effective upon the
earlier of delivery or five (5) days after sending.

Addresses for Notices and Communications Are:

If to the Secured Party:   WorldCom Network Services, Inc.
                           6929 North Lakewood Avenue
                           Tulsa, Oklahoma  74117
                           Attention: Credit and Collections

If to Debtor:              AmeriVision Communications, Inc.
                           5900 Mosteller Drive, Suite 1850
                           Oklahoma City, OK 73112
                           Facsimile No.: (405) 600-3823

         6.2 No Waiver; Cumulative Remedies. Secured Party shall not by any
act, delay, omission or otherwise be deemed to have waived any of its rights or
remedies hereunder, and no waiver shall be valid unless in writing, signed by
Secured Party. A waiver by Secured Party of any right or remedy hereunder on
any one occasion shall not be construed as a bar to any right or remedy which
Secured Party would otherwise have had on any future occasion. The rights and
remedies hereunder provided are cumulative and may be exercised singly or
concurrently, and are not exclusive of any rights or remedies provided by law.

         6.3 Successors and Assigns. All covenants and agreements herein
contained by or on behalf of the Debtor shall bind its successor and assigns
and shall inure to the benefit of the Secured Party and its successors and
assigns. Secured Party's rights under this Agreement or the indebtedness hereby
secured may be assigned from time to time and in any such case the assignee
shall be entitled to all of the rights, privileges and remedies granted in this
Agreement to Secured Party. Debtor may not assign this Agreement or any
instruments or documents executed in connection herewith or any of the rights
of Debtor hereunder without the prior written consent of Secured Party.

         6.4 Governing Law. This Agreement shall be construed in accordance
with and governed by the laws of the State of Oklahoma, without regard to the
conflict of law provisions.

         6.5 Severability. In the event any one or more of the provisions
contained in this Agreement, the Security Instruments, or in any other
instrument or document referred to herein or executed in connection with or as
a security for the TSA, shall, for any reason, be held to be invalid,

                                  Page 7 of 9

<PAGE>   19

illegal or unenforceable, such provision(s) shall not affect any other
provisions of this Agreement, the TSA, the Security Instruments, or any other
instrument or document referred to herein or executed in connection with or as
security for the TSA.

         6.6 Defined Terms. Unless otherwise defined in this Agreement, terms
used in this Agreement which are defined in the applicable Uniform Commercial
Code are used with the meanings as therein defined.

         6.7 Entire Agreement. This Agreement and all instruments, agreements,
and documents attached hereto, referred to herein or executed in connection
herewith, integrate all the terms and conditions mentioned herein or incidental
hereto, constitute the entire agreement between the parties with respect to the
subject matter thereof, and supersede all prior discussions, negotiations and
communication whether oral or written. Neither Secured Party nor Debtor shall
be bound by any promises, representations, warranties, or affirmations not
contained in this Agreement, in an agreement, instrument, or document attached
hereto or referred to herein or executed in connection herewith.

         6.8 Paragraph Headings. Paragraph headings are for reference only and
shall not affect the interpretation or meaning of any provision of this
Agreement.

         6.9 Attorneys' Fees. In the event either party retains the services of
an attorney in any action involving the enforcement of any provision of the
TSA, this Agreement, or any other obligation of Debtor to Secured Party, the
prevailing party as determined by the jurisdiction in which such action is
brought, shall be entitled to reasonable attorneys' fees and other costs,
expenses, and disbursements incurred by the prevailing party in connection
therewith in addition to such other relief as may be available to the
prevailing party.

         SECTION 7.  PRIOR SECURITY AGREEMENT

         The parties acknowledge there currently exists that certain Security
Agreement (the "PRIOR AGREEMENT") dated as of June 1, 1996, by and between
Debtor and Secured Party pursuant to which debtor granted Secured Party a
security interest in certain of its Collateral as defined in such Prior
Agreement. The parties agree that upon the execution and delivery of this
Security Agreement to Secured Party, the Prior Agreement will be canceled and
superseded in its entirety by this Agreement.

                                  Page 8 of 9

<PAGE>   20

         EXECUTED as of the 20th day of April, 1999.

                                         DEBTOR:

                                         AmeriVision Communications, Inc.

                                         By:      /s/ Stephen B. Halliday
                                            ------------------------------------
                                         Title:   President
                                               ---------------------------------
                                         Print Name:       Stephen B. Halliday
                                                    ----------------------------

ATTEST:

Name:
     ------------------------------------

Title:
      -----------------------------------

[SEAL]

                                         SECURED PARTY:

                                         WorldCom Network Services, Inc.

                                         By:      /s/ Robert S. Vetera
                                            ------------------------------------
                                         Title:   Vice President
                                               ---------------------------------
                                         Print Name:       Robert S. Vetera
                                                    ----------------------------

                                         THE UNDERSIGNED HEREBY CONSENTS TO
                                         AMERIVISION COMMUNICATIONS, INC.'S
                                         GRANTING OF THE SECURITY INTEREST TO
                                         WORLDCOM NETWORK SERVICES, INC. AS
                                         SET FORTH IN THIS AGREEMENT:

                                         Coast Business Credit(R), a division of
                                         Southern Pacific Bank

                                         By:
                                            ------------------------------------
                                         Title:
                                               ---------------------------------
                                         Print Name:
                                                    ----------------------------

                                  Page 9 of 9

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