Document:

<PAGE>

                                                                   Exhibit 10.21

                              FIRST AMENDMENT TO
                           MASTER SERVICES AGREEMENT
                                    BETWEEN
                             GTE NETWORK SERVICES
                                      AND
                       GTE GLOBAL NETWORKS INCORPORATED

         THIS FIRST AMENDMENT to the Master Services Agreement (the "Agreement")
is executed by and between GTE Network Services, consisting of the GTE telephone
operating companies listed in Attachment 1 ("GTE") and GTE Global Networks
Incorporated ("GNI"). (GTE and GNI being referred to collectively as the
"Parties".)

                                    RECITALS

WHEREAS, the purpose of this Amendment is to modify the Agreement between the
parties finally executed on September 14, 1999 by modifying the termination
provision thereof and by revising Exhibit B thereto, the Statement of Work (SOW)
to (a) modify the termination provision, (b) include a table of metrics, and (c)
adjust pricing.

WHEREAS, the Parties now wish to adopt the terms set forth below as an amendment
to the Agreement.

NOW, THEREFORE, in consideration of the mutual promises, provisions and
covenants herein contained, the sufficiency of which is hereby acknowledged, the
Parties agree as follows:

         1.       Section 4.2 of the Agreement is deleted and replaced with the
                  following:

                  Notwithstanding anything to the contrary contained in this
                  Agreement, GTE may terminate this Agreement at the expiration
                  of the then current term by providing notice to GNI at least
                  ninety (90) calendar days prior to the expiration of such
                  term. GNI may terminate this Agreement at any time by
                  providing at least ninety (90) calendar days prior written
                  notice of termination to GTE. Termination of the Agreement
                  pursuant to this Section 4.2 shall not be effective as to work
                  under any particular Statement of Work until the earlier of
                  the expiration or termination of such Statement of Work

         2.       A new Section 3.13 is added to the SOW as follows:

                  "The NOC will use commercially reasonable efforts to adhere to
                  the performance metrics set forth in the table of metrics
                  attached hereto as Attachment C and incorporated herein by
                  this reference. These metrics will be used as a method to
                  build historical data. The parties recognize that attainment
                  or non-attainment may be largely subjective. The parties will
                  review and agree to the validity of data used to determine
                  attainment. These metrics are not an unqualified (absolute)
                  measurement or the sole measurement of performance. Attainment
                  or non-attainment of such metrics shall not affect
                  compensation due under this SOW."

                  Attachment 2 hereto, NOC Metrics, is added to the SOW as
                  Attachment C thereto.

         3.       Section 6.0 of the SOW is deleted and replaced with the
                  following:

                  "6.0     Compensation

                                       1
<PAGE>

                  GTE agrees to provide the Services to GNI at the following
                  rates.

                  --------------------------------------------------------------
                  RECURRING COST                                    TOTAL
                  --------------------------------------------------------------
                  GNI NETWORK SUPPORT                         $499,910 PER MONTH
                  --------------------------------------------------------------

                  The labor charges represent the year to year recurring term
                  charges of this SOW unless otherwise negotiated and agreed to
                  by both parties.

                  Notwithstanding anything to the contrary contained in this
                  SOW, Section 6.0, Compensation, is at all times subject to
                  review and modification to conform with any applicable
                  regulatory requirement."

         4.       Section 8.1 of the SOW is deleted and replaced with the
                  following:

                  "Notwithstanding any other provision of this SOW or the
                  Agreement, this SOW is terminable by GNI on ninety (90)
                  calendar days written notice to GTE."

         5.       Except as specifically modified by this First Amendment, the
                  Agreement shall remain in full force and effect.

         6.       If any provision in the Agreement conflicts with this First
                  Amendment, this First Amendment shall control.

                   THE REMAINDER OF THIS PAGE WAS NOT USED.
                  AMENDMENT CONTINUES ON THE SIGNATURE PAGE.

                                       2
<PAGE>

IN WITNESS WHEREOF, the Parties have executed this First Amendment to be
effective on the last date shown below.

GTE Network Services                         GTE Global Networks Incorporated

By:                                          By:
       ____________________________________       ______________________________

Name:    Larry J. Sparrow                    By:
       ____________________________________       ______________________________

Title:   Vice President - Wholesale Markets  Title:
       ____________________________________       ______________________________

Date:                                        Date:
       ____________________________________       ______________________________

By:                                          By:
       __________________________________         ______________________________

Name:    Rosalynn Christian                  Name:  Ondrea Dae Hidley
       __________________________________         ______________________________

Title:   Assistant Secretary                 Title: Assistant Secretary
       __________________________________         ______________________________

Date:                                        Date:
       __________________________________         ______________________________

                                       3
<PAGE>

                                 ATTACHMENT 1
                       GTE TELEPHONE OPERATING COMPANIES

GTE Alaska Incorporated
GTE Arkansas Incorporated
GTE California Incorporated
GTE Florida Incorporated
GTE Hawaiian Telephone Company Incorporated
GTE Midwest Incorporated
GTE North Incorporated
GTE Northwest Incorporated
GTE West Coast Incorporated
GTE South Incorporated
GTE Southwest Incorporated
Contel of Minnesota, Inc. d/b/a GTE Minnesota
Contel of the South, Inc. d/b/a GTE Systems of the South

                                       4
<PAGE>

                           ATTACHMENT 2 TO AMENDMENT
                                 ATTACHMENT C
--------------------------------------------------------------------------------
                                  NOC Metrics
     Note: All agreed upon metrics will be calculated as monthly averages.
--------------------------------------------------------------------------------
1. NOC will troubleshoot and initiate corrective action regarding critical
support system interruptions (those preventing performance of a function) within
two (2) hours.
Comments:
System interruptions may involve processes and work groups beyond NOC control.
NOC must have access to GNI Network.
--------------------------------------------------------------------------------
2. NOC will acknowledge and respond to network events within ten (10) minutes
following event presentation from the network management system.
Comments:
Success in meeting this metric will be determined through a review of a
representative number of trouble tickets compared to the system log.
--------------------------------------------------------------------------------
3. NOC will notify GNI management within fifteen (15) minutes of detecting a
service-affecting event. Notification will be to the specific page list as
defined by GNI according to severity.
Comments:
The NOC currently utilizes a GNI managed support system to deliver this service.
We will continue to utilize this process for notification.
--------------------------------------------------------------------------------
4. NOC will update the Remedy event ticket on critical outages (affecting
customers and requiring immediate attention and dedicated effort to resolve) at
an interval no greater than thirty (30) minutes or upon receipt of information
essential to the event.
Comments:
The current GNI process calls for updating trouble tickets based on the severity
of the event and availability of essential information. We will continue this
practice.
--------------------------------------------------------------------------------
5. NOC will escalate to 2nd level technical support no longer than thirty (30)
minutes following receipt of a critical network event.
Comments:
The current GNI process calls for escalation into 2nd level support based on the
severity of the event. We will continue this practice.
--------------------------------------------------------------------------------
6. NOC will identify customers impacted by a network event notify them within
thirty (30) minutes.
Comments:
Source data will be resident in GNI's Remedy database.
--------------------------------------------------------------------------------
7. NOC will dispatch field personnel within thirty (30) minutes of detecting an
event or receiving another indication of a network event.
Comments:
This timeframe is to allow for 1st and 2nd level support evaluation to determine
need for dispatch.
--------------------------------------------------------------------------------
8. NOC will establish and staff a conference bridge within fifteen (15) minutes
of detecting a service-affecting event (an event affecting network performance
but not customers).
Comments:
Success in meeting this metric will be determined through a review of a sampling
of trouble tickets.
--------------------------------------------------------------------------------
9. NOC will provide initial incident detail within forty eight (48) hours of the
event for input to the GNI led Root Cause Analysis process.
--------------------------------------------------------------------------------

                                       5<PAGE>

                                                                   Exhibit 10.22

                              SECOND AMENDMENT TO
                           MASTER SERVICES AGREEMENT
                                    BETWEEN
                             GTE NETWORK SERVICES
                                      AND
                       GTE GLOBAL NETWORKS INCORPORATED

         THIS SECOND AMENDMENT to the Master Services Agreement (the
"Agreement") effective March 31, 2000 is executed by and between GTE Network
Services, consisting of the GTE telephone operating companies listed in
Attachment 1 ("GTE") and GTE Global Networks Incorporated ("GNI"). (GTE and GNI
being referred to collectively as the "Parties".)

                                    RECITALS

WHEREAS, the purpose of this Amendment is to modify the Agreement between the
parties finally executed on September 14, 1999 by adding a Statement of Work
(SOW) to perform certain services on behalf of GTE Telecom Incorporated,
("Telecom") an affiliate of GNI.

WHEREAS, the Parties now wish to adopt the Statement of Work as an amendment to
the Agreement.

NOW, THEREFORE, in consideration of the mutual promises, provisions and
covenants herein contained, the sufficiency of which is hereby acknowledged, the
Parties agree as follows:

         1.       A new Statement of Work is added as Attachment 2.

         2.       Except as specifically modified by this Second Amendment or
                  prior amendments, the Agreement shall remain in full force and
                  effect.

         3.       If any provision in the Agreement conflicts with this Second
                  Amendment, this Second Amendment shall control.

                   THE REMAINDER OF THIS PAGE WAS NOT USED.
                  AMENDMENT CONTINUES ON THE SIGNATURE PAGE.

                                       1

<PAGE>

IN WITNESS WHEREOF, the Parties have executed this Second Amendment to be
effective as of the date stated in the preamble.

GTE Network Services                        GTE Global Networks Incorporated

By:                                          By:
       ____________________________________       ______________________________

Name:    Larry J. Sparrow                    By:
       ____________________________________       ______________________________

Title:   Vice President - Wholesale Markets  Title:
       ____________________________________       ______________________________

Date:                                        Date:
       ____________________________________       ______________________________

By:                                          By:
       __________________________________         ______________________________

Name:    Rosalynn Christian                  Name:  Ondrea Dae Hidley
       __________________________________         ______________________________

Title:   Assistant Secretary                 Title: Assistant Secretary
       __________________________________         ______________________________

Date:                                        Date:
       __________________________________         ______________________________

                                       2
<PAGE>

                                  ATTACHMENT 1
                        GTE TELEPHONE OPERATING COMPANIES

GTE Alaska Incorporated
GTE Arkansas Incorporated
GTE California Incorporated
GTE Florida Incorporated
GTE Hawaiian Telephone Company Incorporated
GTE Midwest Incorporated
GTE North Incorporated
GTE Northwest Incorporated
GTE West Coast Incorporated
GTE South Incorporated
GTE Southwest Incorporated
Contel of Minnesota, Inc. d/b/a GTE Minnesota
Contel of the South, Inc. d/b/a GTE Systems of the South

                                       3
<PAGE>

                                  ATTACHMENT 2

                          GTE TELECOM STATEMENT OF WORK

This Statement of Work ("SOW") is issued pursuant to the Master Services
Agreement ("MSA") to reflect services to be performed by GTE on behalf of GNI's
affiliate, GTE Telecom Incorporated ("Telecom.")

WHEREAS, GTE and GNI entered into the MSA in order to facilitate the provision
of certain general, administrative, and operational services by GTE; and

WHEREAS, pursuant to that MSA, GNI desires that GTE provides certain Services as
described herein in the support of Telecom's Lease Based Network and Telecom's
Facilities Based Fiber Network (herein collectively referred to as "Telecom's
Network.")

NOW, THEREFORE, GTE and GNI agree as follows:

SECTION 1. - DEFINITIONS.

Many capitalized terms and acronyms appear in this SOW. Unless otherwise
indicated, these terms are understood as having the meanings commonly understood
in the telecommunications industry and in the above referenced Master Services
Agreement. The following less common terms shall have the meanings described:

"DISPATCH" the passing of information to assign task(s) to a specific unit or
send someone on specific business.

"FACILITIES BASED FIBER NETWORK" means the transport mechanism including
elements such as Multiplexers (MUXs"), and Digital Access and Cross-connecting
Systems ("DACs") administrative and management components located in Arkansas,
Illinois, Indiana, and Missouri.

"LEASED BASED NETWORK" means the transport mechanism including elements such as
MUXs, and DACs administrative management components.

"GTE NOC" is the GTE Network Operations Center located at GTE Place at Dallas -
Fort Worth International Airport.

"ON LINE SUPPORT" ("OLS") means call-in or escalated phone support.

                                       4
<PAGE>

"MONITORING AND CONTROL" means twenty four hours a day, seven days a week, three
hundred sixty five days a year ("24 x 7 x 365") near real time fault
surveillance to detect, restore, escalate, and follow-up on anomalies.

"LEVEL 1 TECHNICAL SUPPORT" means work performed by individuals on-site as they
diagnose, isolate, and resolve problems.

"LEVEL 2 TECHNICAL SUPPORT" means support performed by technical experts within
the GTE NOC's On Line Support group. This Service provides phone in assistance
as well as analysis for problems that cannot be resolved at the first level.

"TROUBLE TICKET" means the record of a call or calls from Telecom advising GTE
of a service problem or interruption and a record of all GTE activities relating
to that problem or interruption.

SECTION 2. - MONITORING AND CONTROL TELECOM'S FIBER NETWORK.

GTE NOC will provide 7 x 24 x 365 monitoring and control for the Telecom Network
and its elements including, but not limited to, MUXs, Light Wave Multiplexing
Devices and DACs.

Subject to the terms and conditions contained in this SOW, GTE through its
Network Operations Center ("NOC") will provide Monitoring and Control functions
to include coordination activities related to vendors, customers and field
personnel, Monitoring, Control, and Dispatch of environmental alarms and
Telecom's Network elements including but not limited to MUXs, Light Wave
Multiplexing Devices, and DACs. GTE NOC will also provide trouble isolation,
trouble shooting and Dispatch for the aforementioned functions. A completed
profile for each site listing the network elements and equipment on which the
GTE NOC agrees to provide Service will be provided by Telecom. The functions
will be performed for the equipment and devices contained in centers or
shelters.

SECTION 2.1 - GTE RESPONSIBILITIES.

2.1.1   The NOC will utilize TONICS SNMP and sub-OSS, Systems such as
        Intelligent Alarm Mediator ("IAM") systems to perform Monitoring and
        Control and support functions for Telecom's DAC's, Light Wave
        Multiplexing Equipment, and environmental conditions associated with the
        equipment in Telecom's Network.

2.1.2   The NOC will support the Management Platforms and sub-OSS Systems
        utilized by the NOC to perform monitoring and control functions.

2.1.3   The NOC and Telecom will communicate using a mutually agreed to medium
        regarding change management, outage notification, trouble tickets and
        post mortem issues.

                                       5
<PAGE>

2.1.4   The NOC will provide limited support for Remedy implementation,
        administration and coordination with its other users.

2.1.5   The NOC will coordinate all Dispatches and requests for Telecom and
        other associated units. The NOC will provide technology specific
        resolution to problems and alarms and perform internal escalations to
        include coordination between working units and Dispatch of the
        appropriate field personnel or vendor as necessary. If a problem cannot
        be solved at Level 1, it will be escalated to the appropriate Level 2
        support organization; any personnel providing such support will have
        pagers, cell phones, and remote access capabilities to provide remote
        support. The GTE NOC will participate in and manage bridge calls as
        necessary.

2.1.6   The NOC will provide Telecom with real time access to Trouble Ticket
        System reports for Telecom's Network.

2.1.7   The NOC will propose process improvements and perform required process
        enhancements as the need dictates.

2.1.8   The NOC will coordinate all emergency change management activities as
        requested by Telecom or its authorized representative.

2.1.9   The NOC will participate in post mortem reviews and perform required
        process enhancements.

SECTION 2.2 - GNI RESPONSIBILITIES. Actions to be performed by Telecom shall be
considered responsibilities of GNI for purposes of this SOW.

2.2.1   Telecom will provide the NOC with the required segment/site topology,
        site profiles and equipment lists with all information and drawings to
        facilitate connection, testing and implementation of Monitoring and
        Control processes.

2.2.2   Telecom will ensure proper physical and software maintenance, including
        database records, repair and/or replacement, of the network elements to
        assure proper operation.

2.2.3   Telecom will provide the NOC with the IAM System along with the
        necessary remote access to pertinent surveillance systems.

2.2.4   Telecom will provide complete documentation on all systems and processes
        for carrier escalations.

                                       6
<PAGE>

2.2.5   Upon Telecom's prior approval, Telecom will reasonably fund initial
        training and/or certification requirements necessary to perform NOC
        functions.

2.2.6   Telecom will provide the NOC technicians with read and write
        capabilities into Telecom's network.

2.2.7   Telecom will provide the NOC network connectivity to Telecom's Network.

2.2.8   Once approved by GNI Security, Telecom will provide the NOC access to
        the Network Management and Security Architecture.

2.2.9   Telecom or its authorized representative will lead the change management
        meetings, approve and categorize the changes, publish the ensuing
        schedule, and perform the associated maintenance tasks in the event
        Telecom requests a maintenance or change window.

2.2.10  In the event Telecom becomes aware of a problem with the Telecom
        Network, Telecom will notify the NOC.

SECTION 2.3 - MUTUAL RESPONSIBILITIES.

2.3.1   Prior to initiation of service, the NOC and Telecom Operations will
        conduct and review testing of the operations capability and linkages to
        other Telecom supplier NOCs and Telecom's customer NOCs.

2.3.2   The NOC and Telecom will jointly develop and administer detailed
        interface processes for alarm patterning, assignment of severity levels,
        notification, escalation and personnel contacts.

2.3.3   Changes to the personnel to be contacted shall be provided to the other
        Party no less than seven days prior to the change.

2.3.4   The NOC and Telecom will jointly develop, administer and track Service
        Level objectives as defined in the First Amendment, Attachment 2, to the
        MSA.

SECTION 3. - COMPENSATION.

3.1     Subject to the MSA between the Parties, GTE shall be compensated for the
        Services provided herein as determined by applicable regulatory
        requirements, including requirements regarding affiliate transactions.

3.2     Notwithstanding anything to the contrary contained in this SOW,
        compensation is at all times subject to review and modification to
        conform with any applicable regulatory requirement governing
        transactions between GTE and its affiliates, including without
        limitation FCC docket 96-150.

                                       7
<PAGE>

TABLE 1: TELECOM FIBER NETWORK
<TABLE>
<CAPTION>
--------------------------------------------------------------------------------
           CATEGORY                       ANNUAL                    MONTHLY
--------------------------------------------------------------------------------
<S>                                      <C>                        <C>
LABOR                                    $345,102                   $28,759
--------------------------------------------------------------------------------
TOTAL                                    $345,102                   $28,759
--------------------------------------------------------------------------------
</TABLE>

SECTION 4.  TERM.

4.1     This SOW will become effective upon execution of the Second Amendment to
        the MSA by both Parties and will remain in effect for one (1) year (the
        "Initial Term") and will automatically renew from year to year on the
        anniversary of the execution date ("Renewal Term"), subject to GTE's
        then applicable rates and charges. GTE will provide written notice of
        price changes not less than ninety (90) calendar days prior to the
        renewal date. Either Party may terminate this SOW, effective on
        expiration of the then current term, upon ninety (90) days written
        notice prior to the automatic renewal date.

4.2     Notwithstanding Section 4.1, the term of this SOW and the other terms
        and conditions hereof, are subject to applicable law and regulatory
        approval. Accordingly, although the Second Amendment to the MSA is
        executed by both Parties, to the extent that any state statute, order,
        rule or regulation or any state regulatory agency having competent
        jurisdiction over one or both parties to this SOW or the Second
        Amendment, shall require that this SOW or the Second Amendment be filed
        with or approved by such regulatory agency before the SOW or Second
        Amendment may be effective, this SOW and/or the Second Amendment shall
        not be effective in such state until the first business day after such
        approval or filing shall have occurred.

SECTION 5.  TERMINATION.

5.1     Notwithstanding any other provision of this SOW or the MSA, this SOW is
        terminable by GNI on ninety (90) days written notice to GTE.

5.2     Early termination by GNI shall be subject to the payment of compensation
        for work in progress. In the event of a material default in the
        performance of any of the material obligations of this SOW by either
        Party, the other Party may give the defaulting Party a written notice of
        default and a notice to cure pursuant to Section 19 of the MSA.

5.3     On expiration or termination of the MSA and or this SOW, each Party will
        return all equipment and materials belonging to the other Party in as
        good condition as when received, excepting for normal wear and tear.

                                       8
<PAGE>

SECTION 6. NOTIFICATION AND ESCALATION

In the event either Party fails to perform any materials provision of this SOW,
either Party may give notice to the other Party pursuant to the notice and
escalation provisions set forth in the MSA in Sections 18 and 21 respectively.

Notices to GNI shall be sent to:

GTE GNI
5221 North O'Connor Blvd.
East Tower, 14th Floor
Irving, TX 75039
Attn: Assistant Vice President-Operations

With copies to:

GTE Telecom Incorporated
201 North Franklin, Suite 2400
Tampa, FL 33602
Attn: Manager - Contracts
Fax: 813/209-9620

Escalation points for GNI, via Telecom, are:
Supervisor, Customer Satisfaction Center
Manager, Customer Satisfaction Center
Director, Customer Satisfaction Center
GNI Assistant Vice President- Operations

SECTION 7. REGULATORY COMPLIANCE.

This SOW is subject at all times to any statute, order, rule, or regulation or
any state or federal regulatory agency having competent jurisdiction over one or
both of the parties hereto or the services provided hereby. GTE and GNI agree to
cooperate with each other and with any applicable regulatory agency so that any
and all necessary approvals may be obtained. During the term of this SOW, the
Parties agree to continue to cooperate with each other in any review of this SOW
by a regulatory agency so that the benefits of this SOW may be achieved.

                                       9
<PAGE>

SECTION 8.  PROPRIETARY INFORMATION.

The Parties acknowledge that this SOW constitutes the Proprietary Information of
both Parties and is subject to the terms of the MSA; provided, however that the
Parties further acknowledge that this SOW may be filed with any regulatory
commission having authority over the subject matter, and the parties agree to
seek commercial confidential status for this SOW with any such regulatory
commission, to the extent such a designation can be secured.

                            End of Statement of Work

                                      10

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