<PAGE>   1


                                                                   EXHIBIT 10.20


                        CONFIDENTIAL TREATMENT REQUESTED

                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


                           WALLER CREEK COMMUNICATIONS
                       MASTER SERVICES AGREEMENT WITH I3S

     THIS AGREEMENT (this "Agreement") is entered into by and between Waller
Creek Communications, Incorporated, a Texas corporation having a place of
business at 1801 N. Lamar Blvd., Suite M, Austin, Texas 78701 ("Supplier), and
I3S, a corporation having its principal place of business at 1440 Corporate Dr.
Irving, TX 75038. ("Customer"). This Agreement is effective as of the date of
signature of the last party to sign ("Effective Date").

     WHEREAS, Supplier operates telecommunications facilities in various
metropolitan areas; and

     WHEREAS, Customer desires to have Supplier provide certain
telecommunications services to Customer on its facilities in the geographical
areas served by them; and

     WHEREAS, Supplier desires to facilitate the provision of such services to
Customer; and

     WHEREAS, Customer shall execute its first order of Supplier's services
simultaneous to the execution of this Agreement;

     NOW, THEREFORE, in consideration of the mutual promises and covenants
contained herein, Supplier and Customer agree as follows:



                                       -1-

  THE INFORMATION CONTAINED HEREIN IS CONFIDENTIAL AND PROPRIETARY AND SHOULD
   NOT BE DISCLOSED, COPIED OR DUPLICATED IN ANY MANNER WITHOUT THE WRITTEN
                   PERMISSION OF WALLER CREEK COMMUNICATIONS.
<PAGE>   2


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


1.   DEFINITIONS AND ATTACHMENTS.

     A.   Attachments.

          The following documents are hereby incorporated into and made a part
of this Agreement

          1)   the document entitled "Dedicated Transport Services" which is
               attached hereto and identified as Attachment 1;

          2)   the document entitled "Subunit Capacity Reservations" which is
               attached hereto and identified as Attachment 2;

          3)   the document entitled "Ordering and Billing Procedures" which is
               attached hereto and identified as Attachment 3;

          4)   the document entitled "Technical Specifications" which is
               attached hereto and identified as Attachment 4;

          5)   the document entitled "Trouble Reporting/Maintenance and Repair"
               which is attached hereto and identified as Attachment 5;

          6)   the document entitled "Services Pricing" which is attached hereto
               and identified as Attachment 6; and

          7)   the document entitled "General Provisions" which is attached
               hereto and identified as Attachment 7.

     B.   Definitions.

          The terms used in this Agreement shall have their normal or common
meanings ascribed to them in the telecommunications industry, unless
specifically defined otherwise herein. For purpose of this Agreement, the
following terms shall have the meanings set forth opposite them:

          1)   End User. "End User" shall mean Customer's subscribers to whom
               Customer will provide telecommunications services utilizing, in
               part, Services provided by Supplier to Customer.

          2)   Planned Service Outage. "Planned Service Outage" shall mean a
               complete loss of transmit or receive capability occurring on
               Supplier's network, caused by mutually agreed upon scheduled


                                      -2-
<PAGE>   3


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


               maintenance or planned enhancements or upgrades to either party's
               network.

          3)   Point of Demarcation. "Point of Demarcation" shall mean the
               interface (Customer provided DSX jack or other mutually
               acceptable equipment) between Supplier's and Customer's equipment
               or facilities at Customer's Point of Presence, and the interface
               between Supplier and an End User, Local Exchange Carrier Central
               Office (LEC CO), or an Interexchange Carrier Point of Presence
               (IXC POP).

          4)   Point of Presence. "Point of Presence" or "POP" shall mean a
               specific location where Customer originates and/or terminates its
               telecommunications service.

          5)   Service Date. "Service Date" shall mean the date Service has been
               installed, tested, and is available for Customer's use.

          6)   Service Outage. "Service Outage" shall mean a complete loss of
               transmit or receive capability occurring on Supplier's network,
               excluding: (a) Planned Service Outages; and (b) periods of loss
               due to any Force Majeure Event (as defined in Attachment 7).

          7)   Services. "Services" shall mean dedicated telecommunications
               services, as defined in Attachments 1 and 2, provided by Supplier
               and as specifically identified in ordering forms agreed to
               pursuant to Attachment 3.

          8)   Supplier's Equipment. "Supplier's Equipment" shall mean the
               telecommunications equipment installed, tested, operated and
               controlled by Supplier, necessary for the Services, up to the
               Point of Demarcation.


2.   SERVICES.

     A.   Available Services.

          Supplier shall provide the Services, identified in the initial service
request and any subsequent service requests that are accepted by Supplier, to
Customer for provision of Customer's telecommunications services. Services
shall include normal installation, maintenance, inspection, repair and testing,
as provided for herein. Supplier reserves the right to substitute, change or
rearrange any of Supplier's Equipment, provided that the quality, cost or type
of Services are not adversely affected. Upon mutual agreement of the parties,
the Services may be


                                       -3-
<PAGE>   4


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


changed from time to time during the term of this Agreement to reflect
additional capabilities and features available from Supplier, in which event
this Agreement shall he modified accordingly.

     B.   Additional Services.

          Additional Services that are not described in Attachments 1 and 2 may
be requested by Customer and will be evaluated by Supplier on an individual
case basis.

3.   SERVICE DATE; INSTALLATION.

     Upon completion of installation or connection of facilities and/or
equipment for Customer, Supplier shall conduct appropriate tests to demonstrate
that the Services meet the applicable specifications set forth in Attachment 4.
No Services will be placed upon equipment that has not undergone complete
testing, which includes terminal to terminal testing of fiber optic
transmission systems. Upon successful completion of tests, Supplier shall
verbally notify Customer that such Services are available for use. Supplier
shall make the Services available within the standard installation intervals
agreed to by Supplier and Customer. Supplier shall use good faith reasonable
efforts to make the Services available by the date requested by Customer when
such date is earlier: than the standard interval. In the event that Supplier
delays the provision of a particular Service beyond thirty (30) days after the
Customer-requested date or the standard interval date, whichever is later,
Customer may terminate the affected Service without liability.

4.   ORDERING PROCEDURES.

     Customer and Supplier shall develop mutually agreeable service ordering
procedures pursuant to Attachment 3.

5.   BILLING AND PAYMENT.

     Customer and Supplier shall follow the billing and payment terms,
conditions and procedures set forth in Attachment 3.

6.   CONNECTION


     A.   Connection of Supplier's Equipment and Customer's equipment will be
performed by Supplier. Supplier shall repair or replace, at its sole cost and
expense, any Customer equipment damaged by Supplier, or its agent, during
connection.


     B,   In the event that Customer's or an End User's equipment is not
compatible with a Service ordered by Customer, any special interface equipment
or facilities necessary to achieve compatibility shall be the responsibility of
Customer.


                                       -4-
<PAGE>   5


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


7.   EQUIPMENT AND INSTALLATION

     A.   Unless specifically provided for herein, Supplier, or its agent,
shall, at its sole cost and expense, provide, install, maintain, repair,
operate and control Supplier's Equipment.

     B.   Equipment and service beyond the Point of Demarcation shall be the
responsibility of Customer.

     C.   Customer and the End User shall provide Supplier, at no cost to
Supplier, access to, and reasonable space, power and environmental conditions
at, the Point of Demarcation, including, but not limited to, roof, window,
equipment, battery and conduit space, air conditioning and fire protection, as
applicable for the particular installation. Where the granting of right-of-way
to Supplier to provide such access requires the consent of third parties,
Customer shall use (and shall cause End Users to use) commercially reasonable
efforts to obtain such consent on behalf of Supplier.

     D.   Supplier shall arrange for entry to Customer's POP locally and,
whenever possible, shall provide at least two (2) days notice to Customer prior
to entering Customer's POP to install, maintain or repair any of the
equipment. In the event that it is not possible to provide such notice,
Supplier shall provide notice to Customer as soon as practicable, but in all
events prior to entering the POP.

     E.   Except as set forth in Sections 6.A and 6.B, Supplier shall have no
obligation to install, maintain or repair any equipment owned or provided by
Customer or any End-user.

     F.   If, on responding to a Customer-initiated service call, Supplier and
Customer jointly determine that the cause of the Service deficiency was a
failure, a malfunction or the inadequacy of End User's or Customer's equipment,
Customer shall compensate Supplier, at Supplier's prevailing rates, for actual
time and materials expended during the service call, $150 per hour during 8 a.m.
to 5 p.m., Monday to Friday and $275 per hour on evenings and weekends.

     G.   Neither party shall adjust, align, attempt to repair, relocate or
remove the other party's equipment, except as expressly authorized by the other
party.

     H.   Customer shall be liable for any loss or damage, including theft, to
Supplier's Equipment arising from Customer's or an End User's negligence,
intentional act, willful misconduct or unauthorized maintenance. In the event of
any such loss or damage to Supplier's Equipment, Customer shall reimburse
Supplier for the reasonable cost of repair of Supplier's Equipment, or the
replacement thereof, within thirty (30) days after receipt by Customer of a
written request for reimbursement and substantiation of actual repair or
replacement costs incurred.

     I.   Supplier shall be liable for any loss or damage, including theft, to
Customer's or an End User's equipment arising from Supplier's negligence,
intentional act, willful misconduct, or unauthorized maintenance. In the event
of any such loss or damage to any such equipment, Supplier shall reimburse
Customer or the End User, as the case may be, for the reasonable cost of


                                       -5-
<PAGE>   6


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


repair of the equipment, or the replacement thereof, within thirty (30) days
after receipt by Supplier of a written request for reimbursement and
substantiation of actual repair or replacement costs incurred.

     J.   Supplier's Equipment shall remain the sole and exclusive property of
Supplier, and nothing contained herein shall give or convey to Customer, or any
other person, any right, title or interest whatsoever in Supplier's Equipment.
Supplier's Equipment shall at all times be and remain personal property,
notwithstanding that it may be, or become, attached to, or embedded in, realty.
Customer shall not, and will cause each End User to not, tamper with, remove or
conceal any identifying plates, tags or labels identifying Supplier's ownership
interest in Supplier's Equipment. Customer will not, and will cause End Users to
not, cause to be attached to Supplier's Equipment any liens, security interests
or encumbrances.

     K.   Customer's equipment shall remain the sole and exclusive property of
Customer, and nothing contained herein shall give or convey to Supplier, or any
other person, any right, title or interest whatsoever in Customer's equipment.
Customer's equipment shall at all times be and remain personal property,
notwithstanding that it may be, or become, attached to, or embedded in, realty.
Supplier shall not tamper with, remove or conceal any identifying plates, tags
or labels identifying Customer's ownership interest in Customer's equipment.
Supplier will not cause to be attached to Customer's equipment any liens,
security interests or encumbrances.

8.   TROUBLE REPORTING; MAINTENANCE.

     The parties shall follow the trouble reporting procedures described in
Attachment 5. Supplier shall properly maintain the Supplier Equipment used to
provide the Services, at no additional charge to Customer.

9.   TERM/TERMINATION LIABILITY.

     This Agreement shall be in effect for a period of 3 year(s) from the
Effective Date and shall thereafter continue in effect on a year-to-year basis
unless terminated by either party upon ninety (90) days advance written notice
to the other. Upon termination of this Agreement, all rights of Customer to
order new Services shall cease and Supplier shall have no further obligations to
furnish new Services to Customer. In the event of termination of this Agreement.
Services not previously terminated by Customer shall remain in effect for the
term specified in the applicable service request, and the terms and conditions
of this Agreement shall continue to apply to such Services. The Services are
provided on a "take-or-pay" basis, based on the Services ordered by Customer and
ramp-up schedule included in Attachment 6.


                                       -6-
<PAGE>   7


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


10.  GOVERNMENTAL AUTHORIZATION.

     This Agreement is subject to all applicable federal, state and local laws,
and regulations, rulings, orders and other actions of governmental agencies
("Rules"), including, but not limited to, the Communications Act of 1934, as
amended, the rules and regulations of the Federal Communications Commission
("FCC"), and the obtaining and continuance of any required approval or
authorization of the FCC or any governmental body. Supplier shall use its good
faith reasonable efforts to obtain, retain, and maintain such approvals and
authorizations. If any such Rule adversely affects the Services or requires
Supplier to provide such Services other than in accordance with the terms of
this Agreement, either party may, without liability to the other party,
terminate the affected Service upon prior written notice to the other party.

11.  SERVICE GUARANTEES.

     A.   Out-of-Service Credits.

          1) A credit allowance will be given for Service Outages as specified
below. Credit allowances will be expressly indicated and deducted from
Customer's next invoice. A Service Outage begins (for service guaranty) when
Customer reports the Service malfunction to Supplier and the location of the
cause of the Service Outage is determined. A Service Outage ends when the
affected circuit is fully operational and accepted by Customer. A credit will be
given for the time the service outage began until it ended.

          2) Out-of-service credits do not apply to Service Outages: (a) caused
by Customer or an End User or a supplier of service to Supplier, i.e. the
Incumbent Local Exchange Carrier; (b) due to failure of power or equipment
provided by Customer or other third parties; (c) during any period in which
Supplier is not given access to the Service premises; (d) which constitute
Planned Service Outages; and (e) due to any Force Majeure Event (as defined in
Attachment 7).

     B.   Chronic Trouble Service.

          A "chronic trouble service" is a particular Service for which two or
more trouble tickets have been opened within a 30-day period and the cause of
each such trouble is determined to be in Supplier's network.

          Whenever Customer reports to Supplier that a Dedicated Transport
Service is a chronic trouble service, Supplier shall immediately perform a
detailed investigation and report the findings to Customer. In the event that
another trouble ticket is opened on such Service within a 30-day period after
clearing the most-recent trouble, Customer may disconnect such specific Service
without incurring termination liability. Supplier has no obligation to provide
alternative routing for any transmission capacity provided pursuant to this
Agreement.


                                      -7-
<PAGE>   8


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


12.  DEFAULT.


     Except for Supplier's obligations to furnish the Services without
interruption, the sole remedies for breach of which obligations are provided for
in Sections II.A. and II.C. herein, and Supplier's obligations to install the
Service by a given date, the sole remedies for breach of which obligations are
provided for in Sections 3 and 11.B. herein, neither party shall be in default
under this Agreement or in breach of any provisions hereof unless and until it
has been given written notice of a breach of this Agreement by the other party
and shall have failed to cure such breach within 30-day period after receipt of
such notice. When a breach cannot reasonably be cured within such 30-day period,
if the breaching party shall proceed promptly to cure the same and prosecute
such curing with due diligence, the time for curing such breach shall be
extended for such reasonable period of time as may be necessary to complete
such curing. Upon the failure to so cure any such breach which is material, the
party giving notice of the material breach may thereupon immediately terminate
this Agreement by providing written notice of termination to the breaching party
and, when Customer is the non-breaching party, without incurring any termination
liability. When Customer is the breaching party, Customer shall be liable for
all termination liability imposed hereunder if Supplier exercises its right to
terminate this Agreement. Except as specifically set forth herein and subject to
the provisions of Attachment 7, "Arbitration," upon default by either party, the
non-defaulting party shall have the right to pursue any or all remedies
available at law and/or equity.

13.  MISCELLANEOUS.

     This Agreement (including the incorporated Attachments) constitutes the
entire agreement between Supplier and Customer with respect to the Services; all
prior and contemporaneous agreements, representations, statements, negotiations,
and undertakings with respect to the subject matter herein are superseded by
this Agreement. THERE ARE NO AGREEMENTS, WARRANTIES, OR REPRESENTATIONS,
EXPRESS OR IMPLIED, EITHER IN FACT OR BY OPERATION OF LAW, STATUTORY OR
OTHERWISE, INCLUDING WITHOUT LIMITATION WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE OR USE, EXCEPT THOSE EXPRESSLY SET FORTH
HEREIN. Neither this Agreement nor any of the provisions hereof may be amended,
altered or added to in any manner except by a document in writing and signed by
an authorized representative of each party.


     IN WITNESS WHEREOF, the parties have caused this Agreement to be executed
by their duly authorized representatives.

"SUPPLIER"                                   "CUSTOMER"
----------                                   ----------
WALLER CREEK COMMUNICATIONS                  I3S

By: /s/ [ILLEGIBLE]                          By: /s/ [ILLEGIBLE]
    ------------------------                     -------------------------------
Title: Chairman                              Title: VP Engineering

Dare:   6/17/99                              Date: 6-18-99


                                      -8-
<PAGE>   9


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


                                  Attachment 1

                          DEDICATED TRANSPORT SERVICES
                             SERVICE DESCRIPTIONS


DEDICATED

Each transport Service is dedicated to Customer and is billed a fixed amount
monthly. The entire usable bandwidth for each Service is available to Customer
or its customers for its exclusive use, twenty-four (24) hours a day, seven (7)
days a week.

POINT-TO-POINT

Dedicated Transport Services are available between Customer-designated
locations on a virtual hub point-to-point basis. Virtual Hub Service allows
Customer to aggregate multiple lower capacity transport Services terminating at
multiple locations onto one higher capacity Service terminating at one other
Customer location.

Service may be ordered between Customer's Point of Presence and an End User
("EU") location, between two Customer POP's, between a Customer POP and a LEC
CO, between a customer POP and an IXC POP, or between two EU locations.

CUSTOM SERVICES

Dedicated Transport Services or non-standard configurations not described above
will be evaluated on an Individual Case Basis (ICB).


                                      -9-
<PAGE>   10


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT

                                  Attachment 2


                         SUBUNIT CAPACITY RESERVATIONS:
                               SERVICE DESCRIPTION


NOT APPLICABLE


                                      -10-
<PAGE>   11


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT

                                  Attachment 3

                          ORDERING & BILLING PROCEDURES


A.   ORDERING VEHICLE.

Initially, orders will be placed through Local Account Executive VIA facsimile.
The parties may mutually establish an interface which allows for "bonded"
ordering by the customer.

B.   SERVICE ORDER INTERVALS.

Supplier and Customer will negotiate mutually agreeable service ordering forms
and intervals, and make good faith efforts to establish electronic bonding
arrangements for all ordering and provisioning.

C.   STANDARD INSTALLATION INTERVALS

The standard installation interval for all Dedicated Transport Services will be
eleven (11) calendar days. Supplier will provide Service on an individual case
basis based on the requirements and expectations of Customer, as follows: if an
installation interval is requested that is less that the standard eleven (11)
calendar days, Supplier will use good faith reasonable efforts to meet the
requested start of service date, and if Supplier cannot meet the requested start
of service date, then it will negotiate in good faith the earliest start of
service date possible with Customer.

D.   BILLING AND PAYMENT

Supplier shall be entitled to commence billing Customer as of the Service Date.
Non-recurring charges shall be paid upon Customer's acceptance of this
Agreement. In the event that Customer delays the use of a particular Service, an
order changing the due date must be issued prior to the original due date, and
be no more than thirty (30) days after the original requested Date, Supplier may
commence billing Customer for the affected Service as of the 31st day of such
change. Supplier shall bill on a current basis all charges incurred by and
credits due to Customer. Customer may receive its bill in 1) a paper format, 2)
a paper format bill summary with a magnetic tape to provide the detailed
information of the bill, 3) magnetic tape only, or a 4) computer disc. Supplier
shall bill in advance charges for all Services to be provided during the ensuing
billing period except for charges associated with Service usage. Adjustments for
the quantities of Services established or discontinued in any billing period
beyond the minimum period established in the FCC tariff 1 will be prorated to
the number of days based on a 30-day month. Supplier will, upon request and if
available, furnish such detailed information as may reasonably be required for
verification of bills.


                                      -11-
<PAGE>   12


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


All bills for Services provided to Customer by Supplier are due (payment date)
by the next bill date, regardless of the bill media utilized, and are payable in
immediately available funds. If such payment due date would cause payment to be
due on a Saturday, Sunday or legal holiday, payment for such bills will be due
on the last business day preceding such Saturday, Sunday, or legal holiday.

If any portion of the payment is received by Supplier after the payment due
date, or if any portion of the payment is received by Supplier in funds which
are not immediately available to Supplier, then interest on the overdue amounts
shall accrue and be payable by Customer at a rate of 1.5% per month (.000494 per
day) or 18% annually or, if less, the maximum rate permitted by applicable law.
The interest will be applied for the number of days from the payment due date
to and including the date that Supplier actually receives the payment.

E.   CLAIMS AND DISPUTES

In the event that a billing dispute occurs concerning any charges billed to
Customer by Supplier, Customer must submit a documented claim for the disputed
amount. Customer will submit all documentation as may reasonably be required to
support the claim. All claims must be submitted to Supplier within one hundred
and twenty (120) days of receipt of billing for those Services. If Customer does
not submit a claim as stated above, Customer waives all rights to file a claim
thereafter.

If the dispute is resolved in favor of Customer and Customer has withheld the
disputed amount, no interest credits or penalties will apply.

If the dispute is resolved in favor of Customer and Customer has paid the
disputed amount, Customer will be credited with interest on such amount by
Supplier at the rate of 1.5% per month (.000494 per day) or 18% annually or, if
less, the maximum rate permitted by law, from the date Supplier received payment
up to and including the date of refund.

If the dispute is resolved in favor of Supplier and Customer has paid the
disputed amount on or before the payment due date, no interest credit or
penalties will apply.

If the dispute is resolved in favor of Supplier and Customer has withheld the
disputed amount, any payments withheld pending settlement of the disputed amount
shall bear interest at the rate of 1.5% per month (.000494 per day) or 18%
annually or, if less, the maximum rate permitted by law, from the payment due
date up to and including the date of payment.


                                      -12-
<PAGE>   13


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT

                                  Attachment 4

                            TECHNICAL SPECIFICATIONS

This Attachment provides transmission performance objectives for point-to-point
DS3 and DS1 covering the bi-directional path between two points of termination
("POT").

The transmission performance objectives specified in this standard are based on
End User needs and applications, characteristics of voiceband data modems, and
capabilities of evolving SONET networks. The objectives are considered to be
reasonable criteria for circuit acceptance and restoral.

DS-1 SERVICE

Offered via SONET Networks

A 1.544 Mbps circuit which can accommodate either clear channel B8ZS or
channelized (24 DS-1 channels) AMI, Superframe or Extended Superframe format.

o    Availability              o    > or = 99.99% measured annually
o    Bit Error Rate (BER)*     o    < or = 1Xl0(-9)
o    Error Free Seconds        o    > or = 99.999% measured annually
o    Line Code                           AMI or B8ZS
o    Frame Format              o    Superframe (SF) or Extended Superframe (ESF)
o    Mean Time to Repair       o    2 hours


DS-3 SERVICE

Offered via SONET Networks

A 44.736 Mbps circuit which can accommodate either clear channel unframed or
B3ZS (28 DS1's, or combinations of DS-1s, DS-2s and/or DS-3s).

o    Availability                       > or = 99.99% Annually
o    Bit Error Rate (BER)*              < or = 1X10(-9)
o    Error Free Seconds                 > or = 99.999% Annually
o    Line Code                                   B3ZS
o    Frame Format                       C-Bit or M13
o    Mean Time to Repair                2 hours



                                      -13-
<PAGE>   14


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


                                  Attachment 5

                    TROUBLE REPORTING/MAINTENANCE AND REPAIR

Supplier shall maintain a twenty-four (24) hours a day, seven (7) days a week
point-of-contact for Customer to report to Supplier system trouble reports or
faults. Supplier shall furnish Customer a toll-tree trouble reporting telephone
number that will provide access to Supplier on a 24x7x365 basis.

Supplier shall perform all maintenance functions on Services from the End User
premises to the Point of Demarcation at Customer's facilities twenty-four (24)
hours per day, seven (7) days a week.

REPAIR REPORTING AND REPAIR INTERVALS

Supplier will establish a process with Customer to accept reports relating to
repair or maintenance associated with Services provided by Supplier to Customer.

SCHEDULED MAINTENANCE

Scheduled routine maintenance will be performed during specified Customer
maintenance windows and will be coordinated between Supplier and Customer.

Maintenance which may place the Services in jeopardy or require system down
time will normally be performed during a "Maintenance Window" that is mutually
agreed to between Customer and Supplier. Jeopardy and down time must be
requested by Supplier to Customer within a negotiated time frame as not to
jeopardize Customer's network operations.

Supplier maintenance personnel will notify Customer prior to beginning scheduled
maintenance work and must receive concurrence to proceed.

SYSTEM RESTORATION

Electronic restoration - In the event of an electronic failure, Supplier shall
restore Services to the affected electronics within one and one-half (1.5) hours
of arrival of Supplier's maintenance personnel on site.

Cable restoration - In the event of a cable failure, Supplier shall begin cable
restoration within two (2) hours after the faulty cable is identified. The
failed cable shall be restored not later than four (4) hours after such
identification.


                                      -14-
<PAGE>   15


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


                                  Attachment 6

                                SERVICES PRICING


Supplier shall offer Customer services according the following terms.

MONTHLY RECURRING CHARGES

Recurring charges are based on the number of T-1 equivalents Customer commits
to purchase according to the tiers and ramp-up schedule below, and are assessed
on a "take-or-pay" basis. The monthly recurring rates per T-1 are listed below
as fixed prices per T1. Each T1 provided with DACS and MUXing services by
Supplier will cost an additional * per T1 per month. Fractional months will be
pro-rated based on a 30-day calendar month.

<TABLE>
<CAPTION>
                           3 Year
                           ------
<S>                        <C>
> or = 1000 OPTION            *
> or = 500 & < 1000           *
> or = 100 and < 500 Option   *
</TABLE>

For On-Net Customer ordered services at a DS-3 level, one DS-3 shall be priced
at * times the applicable monthly recurring T-1 price, and one OC-3 shall be
priced at * times the applicable monthly recurring T-1 price. "On-Net Services"
are defined as services to locations where Supplier provides the fiber
transmission medium.

For Off-Net Customer ordered services at a DS-3 level, one DS-3 shall be priced
at * times the applicable monthly recurring T-1 price, and one OC-3 shall be
priced at * times the applicable monthly recurring T-1 price. "Off-Net
Services" are defined as services to locations where Supplier does not provide
the fiber transmission medium.

NON-RECURRING CHARGES

Initial non-recurring charges are assessed at the turn-up of a circuit
purchased by Customer. Initial non-recurring charges are assessed on a per T-1
basis, depending on the contract term, as follows:

<TABLE>
<CAPTION>
                                3 Year
                                ------
<S>                             <C>
Initial NRC T-1                   *

Initial NRC for DS-3              *
Initial NRC OC-3                  *
</TABLE>


                                      -15-
<PAGE>   16


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


RAMP-UP PERIOD


Customer has a period of 1 year from the date of this Agreement to reach the
committed level of T-1, or T-1 equivalent circuits, provided however, Supplier
activates the Dallas, TX., Ft. Worth, TX., and San Antonio, TX networks before
12/31/99 and Houston, TX network before 3/31/00. If Supplier does activate
these additional markets per this timeline, Customer ramp-up period will
extended for a period of 6 months after all 5 markets are active (Austin,
Dallas, Ft. Worth, San Antonio, Houston). The committed level of T-1 or T-1
equivalent services is 100.


PRICING CONDITIONS

o    Customer will not be bound by a contract term for any single T1 or T1
     equivalent circuit. The term of this agreement commits Customer to a bulk
     number of T1 or T1 equivalent circuits per month over the contract
     period. Customer compliance will be determined by the number of T1 or T1
     equivalent circuits active on the 30th of each month.

o    All "A to Z" circuits ordered by Customer in a city shall originate from a
     single "A" location (i.e., Customer's POP). "Z" locations are available to
     any location in the city where services are available.

o    Supplier's commitment to delivery of DS-3 and OC-3 circuits shall be
     subject to availability in the city in which they are requested by
     Customer.


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<PAGE>   17


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


                                  Attachment 7

                               GENERAL PROVISIONS

ARBITRATION: Subject to a party's right to terminate this Agreement pursuant to
Section 12, any dispute arising between Supplier and Customer in connection with
this Agreement, which is not settled to the mutual satisfaction of Customer and
Supplier within thirty (30) days (or such longer period as may be mutually
agreed upon) from the date that either party informs the other in writing that
such dispute or disagreement exists, shall be settled by arbitration conducted
in Austin, Texas in accordance with the Commercial Arbitration Rules of the
American Arbitration Association in effect on the date that such notice is
given. The decision of the arbitrator shall be final and binding upon the
parties and judgment may be obtained thereon by either party in a court of
competent jurisdiction. Each party shall bear the cost of preparing and
presenting its case. The cost of arbitration, including the fees and expenses of
the arbitrator, will be shared equally by the parties unless the award otherwise
provides.

ASSIGNMENT: Neither party may specifically and independently assign this
Agreement without the prior written consent of the other party, which consent
shall not be unreasonably withheld, delayed or conditioned; provided, however,
that upon notice, Supplier may assign this Agreement without consent, to any
affiliated entity or successor in interest, whether by merger, reorganization,
or transfer of all or substantially all of its assets. Customer may assign this
Agreement upon notice to Supplier, to any affiliated entity or successor in
interest, whether by merger, reorganization, or transfer of all or
substantially all of its assets provided that the assignee has the financial
resources to meet the payment obligations under this Agreement and expressly
agrees in writing to assume those obligations. Upon receipt of such notice, in
the event Supplier, in its sole discretion, reasonably determines the assignee
does not have the financial resources necessary to meet the payment obligations
hereunder, then any such assignment shall he null and void and Customer shall
remain fully responsible for the obligations under the Agreement.


BANKRUPTCY: If any of the following occurs with respect to either party
("Affected Party"), such party shall be in breach of this Agreement: (i) the
initiation of proceedings by the Affected Party in voluntary bankruptcy; (ii)
the initiation of proceedings against the Affected Party in involuntary
bankruptcy, which proceedings are not dismissed or vacated within ninety (90)
days after their initiation; (iii) the appointment of a receiver or trustee for
the Affected Party; (iv) a general assignment for the benefit of the Affected
Party's creditors; or (v) the insolvency of the Affected Party.


COMPLIANCE WITH LAWS: In performing their obligations under this Agreement, the
parties shall comply with all applicable federal, state, and local laws,
regulations, rules and orders.

CONFIDENTIALITY: Each party may, either orally, in written form, or otherwise,
disclose to the other party, or the other party may otherwise obtain the
disclosing party's, confidential information ("Confidential Information") in
connection with this Agreement. The terms and conditions of this Agreement are
Confidential Information, except that either party shall have the right to
disclose the terms and conditions of this Agreement to its affiliates, provided
that such


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<PAGE>   18


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


affiliates agree to be bound by the provisions of this section. In order to be
Confidential Information, any information disclosed in a tangible form must he
conspicuously marked as being the disclosing party's confidential information,
and any other information must be clearly indicated as being confidential at the
time of disclosure and confirmed as such in writing within ten (10) days after
disclosure; provided, however, that any information that a party may disclose
to the other party, or that a party may otherwise obtain concerning the other
party, in connection with this Agreement, regarding either (a) its business
plan, (b) a party's existing or potential customers, or (c) its networks and
technology, including without limitation, information regarding routing of End
Users' traffic over such networks and existing network hardware and facility
configurations and plans for modifying such configurations, shall be
Confidential Information regardless of whether it is indicated as such at the
time of disclosure, and if it is orally disclosed, regardless of whether it is
subsequently confirmed as such in writing. Regardless of when disclosed or
obtained, Confidential Information shall only be used by the receiving party in
its performance hereunder, and it shall not be disclosed by the receiving party,
except to those officers, directors or employees of the receiving party or its
affiliates with a need to know or to consultants or subcontractors of the
receiving party that have entered into a confidentiality agreement with the
receiving party with respect to the Confidential Information that is at least as
restrictive as this Agreement. If any of the following apply to any information,
such information shall not be Confidential Information: (i) it is or becomes
available to the public through no wrongful act of the receiving party; (ii) it
is already in the possession of the receiving party and not subject to any
prior agreement of confidence between the parties; (iii) it is received by the
receiving party from a third party without restriction for the benefit of the
disclosing party and without breach of this Agreement; (iv) it is independently
developed by the receiving party without regard to any Confidential Information
of the disclosing party: (v) it is disclosed by the receiving party pursuant to
a requirement of a duly empowered government agency or a court of competent
jurisdiction after due notice and an adequate opportunity to intervene is given
to the disclosing party unless such notice is prohibited. Upon termination or
expiration of this Agreement (or the last ASR in effect, if later), the
receiving party shall, at the disclosing party's direction, either return to the
disclosing party or destroy all of the disclosing party's Confidential
Information and so certify in writing. The obligations of this provision will
survive for two (2) years after any termination or expiration of this Agreement
(or the last ASR in effect, if later).

DELAY: Whenever any actual or potential event is delaying or threatening to
delay or interfere with the delivery of Services, Supplier shall so notify
Customer in writing as soon as practicable; provided, however, that such notice
to Customer shall not limit Supplier's obligations to perform under this
Agreement.

FORCE MAJEURE: Supplier shall not be liable or deemed to be in default for any
delay, interruption, or failure in performance under this Agreement resulting
from the following events: acts of God; acts of civil or military authority;
acts of the public enemy; war; accidents, fires, explosions, power surges,
earthquakes, floods, or unusually severe weather; strikes or labor disputes;
delays in transportation or delivery outside the reasonable control of Supplier;
epidemics; and any similar event beyond Supplier's reasonable control ("Force
Majeure Event"). In the event of such delay, interruption, or failure in
performance, Supplier shall as soon as practicable give written notice to
Customer specifying the nature and anticipated duration of the


                                      -18-
<PAGE>   19


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT



Force Majeure Event and outlining its recovery plan, if any, Customer may
terminate all or any portion of the affected Services if a Force Majeure Event
continues for sixty (60) days. In the event of such a termination, Customer
shall only be obligated to pay for Services performed through the date of
termination and shall receive from Supplier a full refund of any prepaid
Services not provided by Supplier.


GOVERNING LAW: This Agreement is governed by and subject to the law of the State
of Texas.

INDEMNIFICATION: Each party ("Indemnitor") shall defend, hold harmless, and
indemnify the other and its parent company, affiliates, employees, directors,
officers, partners, and agents (each, an "Indemnitee") from and against all
claims, actions, damages, liabilities, payments made in settlement, costs and
expenses, including reasonable attorneys' fees and expenses, for Indemnitor's
breach of this Agreement, or for damages to any property or bodily injury to or
death of any person arising due to Indemnitor's negligence or willful
misconduct. This provision shall survive the termination or expiration or this
Agreement.

INDEPENDENT CONTRACTORS: The relationship between Supplier and Customer
shall always and only be that of independent contractors.

INFRINGEMENT: Supplier shall defend, indemnify and hold Customer harmless from
and against any claim, suit, or proceeding brought against Customer for any
loss, damage, expense (including reasonable attorneys' fees) or liability
insofar as such claim, suit or proceeding is based upon a claim that Customer's
use of any Services provided by Supplier infringes or constitutes a wrongful use
of any United States patent, or any copyright, trade secret or other
intellectual property right of a third party which is enforceable in the United
States ("Infringement Claim"). Customer shall give Supplier prompt written
notice of any such claim or action. Customer shall give Supplier proper and full
information and assistance to defend or settle any such claim or action. At
Supplier's option, Supplier shall have full control over all of the defenses of
any such action, suit or proceeding. Should Customer desire to have its own
counsel participate in any such claim or action, the cost of such counsel shall
be borne by Customer. If an injunction or order is obtained against Customer's
continued use of the Services due to an Infringement Claim, Supplier shall, at
its expense, use commercially reasonable efforts to either procure for Customer
the right to continue using the infringing Services or replace or modify the
infringing Services in a reasonable manner so that they become non-infringing,
provided that any such modification or replacement does not adversely affect the
functional performance of Customer's use of the Services or, at Customer's
option, cease providing the Services if it is not possible to reasonably modify
or replace the same, in which case Customer shall have no termination liability
with respect to such Services. Notwithstanding the foregoing, Supplier shall
have no obligation to defend or hold harmless Customer against, and shall have
no liability for, any claim based upon the use of the Services with any services
or products not supplied by Supplier if such infringement would have been
avoided by the use of the Services without such other services or products, or
for any claim based upon a modification to the Services made by any party other
than Supplier. This provision shall survive the termination or expiration of
this Agreement.


                                      - 19-
<PAGE>   20



                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


INSURANCE: Supplier shall obtain and maintain, at all times during which it is
providing Services hereunder, insurance policies of the kinds and in the
amounts not less than that required by the following or, if greater, by
applicable law:

     A.   Worker's Compensation Insurance in accordance with the Worker's
Compensation Laws of the states in which Services are provided;

     B.   Commercial General Liability Insurance, including automobile
insurance, contractual and products/completed operations liability coverage,
with minimum limits as follows:

          bodily injury to any one person               $1,000,000

          bodily injury aggregate per occurrence        $1,000,000

          property damage in any one accident           $  500,000

          property damages aggregate
          per occurrence                                $1,000,000

Upon request of Customer, Supplier shall furnish Customer certificates of such
insurance as proof of coverage and name Customer as loss payee in connection
therewith. Supplier shall use good faith reasonable efforts to notify Customer
no less than thirty (30) days prior to reduction in limits or cancellation of
such insurance.

LIMITATION OF LIABILITY: In no event shall either party be liable to the other
party for any indirect, consequential, special, incidental, reliance, or
punitive damages of any kind or nature whatsoever (including without limitation
lost profits, lost revenues, lost savings, or harm to business), whether or not
foreseeable, whether or not Supplier or Customer had or should have had any
knowledge, actual or constructive, that such damages might be incurred, and
regardless of the form of action. For purposes of this Agreement, damages of
the kinds specified in the preceding sentence which are incurred by a third
party and assessed against Supplier or Customer (including attorneys' fees and
expenses) shall be deemed indirect damages to Supplier or Customer, as
applicable. Each party hereby releases the other party (and such party's
subsidiaries and affiliates, and their respective officers, directors,
partners, employees, agents, and suppliers) from any such claim.

NON-EXCLUSIVE ARRANGEMENT: This Agreement between Supplier and Customer is
non-exclusive. Nothing in this Agreement shall prevent Supplier or Customer from
entering into similar arrangements with any other entities or otherwise
providing services to any entity.

NON-WAIVER: Either party's failure to insist upon strict performance of the
terms of this Agreement or to exercise any rights or remedies hereunder shall
not waive any of its rights to require strict performance of such terms, to
assert any of the same rights, or to rely on any such terms any time thereafter.


                                      -20-
<PAGE>   21


                                                     WALLER CREEK COMMUNICATIONS
                                                       MASTER SERVICES AGREEMENT


NOTICES: Any notice and similar communications given under this Agreement shall
be in writing, and shall be delivered to the receiving party (i) in person, (ii)
by certified mail with return receipt requested, (iii) by overnight carrier, or
(iv) by facsimile, electronically confirmed and followed up immediately by
regular mail. Notices shall be delivered or sent to the parties' respective
addresses set forth elsewhere in this Agreement or to such other address as the
receiving party may hereafter establish by notice given in the manner prescribed
in this paragraph. A notice shall be deemed given when delivered, if personally
delivered, at the time indicated on the return receipt, if delivered by
certified mail, on the next business day, if delivered via courier, or when
transmitted, if delivered via facsimile.

SEVERABILITY: In the event that one or more of the provisions herein shall for
any reason be held to be illegal or unenforceable, this Agreement shall be
revised only to the extent necessary to make such provision(s) legal and
enforceable; provided, however, that the Agreement, as revised, is consistent
with the parties' original intent.

SURVIVAL: The terms and conditions of this Agreement shall survive the
expiration or termination of this Agreement to the full extent necessary for
their enforcement and for the realization of the benefit thereof by the party in
whose favor they operate.

TAXES: The prices stated in this Agreement do not include any applicable
federal, state, or local taxes. Unless Customer is exempt, Customer shall pay
such applicable taxes upon receipt of an itemized invoice therefor. Customer
shall provide Supplier with appropriate documentation of any exemption.


                                      -21-