<PAGE>
                                                                   Exhibit 10.19




                               THIRD AMENDMENT TO
                            MASTER SERVICES AGREEMENT

         This Third Amendment ("Third Amendment") is effective as of the first
day of July, 2000 ("Third Amendment Effective Date") and amends and supplements
that certain Master Services Agreement, as amended (the "Agreement") dated as of
the 9th day of December, 1999, by and between VALOR TELECOMMUNICATIONS
ENTERPRISES, LLC (as successor to Valor TeJecommtmications Southwest, LLC,
successor to dba Communications LLC) ("Client") and ALLTEL INFORMATION SERVICES,
INC. ("ALLTEL").

                                   WITNESSETH:

         WHEREAS, Client desires to obtain additional services from ALLTEL and
ALLTEL is willing to provide such services pursuant to the terms and conditions
contained herein;

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

1.       The following ALLTEL Software shall be added to Exhibit H of the
         Agreement:

<TABLE>
<S>                         <C>                 <C>
Wireline Billing            PASP                Reads 9201 Toll Records; Creates
                                                9299 Summary Records"
</TABLE>

2.       The following ALLTEL-Provided Third Party Software shall be added to
         Exhibit I of the Agreement:

<TABLE>
<S>                 <C>                  <C>                        <C>
Wireline
Operation           Connect-Direct       Internal File Transfer     Sterling Software"
</TABLE>

3.       The following new Section 5 shall be added to Exhibit A to the
         Agreement:

         "5.      PASP SERVICES. ALL TEL shall use the PASP application
                  (identified as ALLTEL Software in Exhibit H) to create "type
                  9299" summary records for Client's Access Lines located in
                  Oklahoma and Texas ("PASP Services"). The PASP application is
                  an AS/400 based wireline clearinghouse-Hke application that
                  reads "type 9201" records from ALLTEL's Customer Account
                  Management System (CAMS) and creates "type 9299" summary
                  records. Type 9201 records are toll detail records containing
                  among other information, originating NPA-NXX, tenninating
                  NPA-NXX, and call duration. By processing these 9201 toll
                  detail records through the PASP application and referencing a
                  number of tables, PASP creates 9299 summary records. These
                  9299 summary records contain an originating NPA-NXX, and
                  originating CLLI code, a terminating NPA-NXX, a

                                        1
<PAGE>

                  tenninating CLLI code and up to eight (8) transiting NECA
                  codes. These NECA codes identify ownership based upon call
                  paths and distribute that information to each owner. This will
                  provide Client the ability to bill other telcos based upon the
                  amount of time Client carried such other telcos' toll calls."

4.       The following new Section 2.5 shall be added to Exhibit E to the
         Agreement

         "2 5     FEES FOR PASP SERVICES. Commencing August 1, 2000, Client
                  shall pay the following Service Fees for PASP Services:

<TABLE>
<S>                         <C>
Monthly Service Fees        $[*****]
</TABLE>

                  The Service Fees for PASP Services are based upon processing
                  for the number of Client Access Lines in Texas and Oklahoma as
                  of the Managed Operations Conunencemcnt Date (approximately
                  440,000 Access Lines). Should Client acquire additional
                  properties with PASP processing requirements or should the
                  number of Access Lines in Texas and Oklahoma with PASP
                  processing requirements exceed 500,000 Access Lines, ALLTEL
                  reserves the right to increase the monthly Service Fees for
                  PASP Services in proportion to the increase in the number of
                  Access Lines with PASP processing requirements.

                  In connection with the PASP Services, Client shall pay
                  Pass-Through Expenses for the initial purchase of tape
                  inventory and monthly shipping costs."

5.       Section 8 of Exhibit E to the Agreement shall be amended as follows
         (with strikethroughs indicating deletions and double underlining
         indicating additions):

         "8.      COST OF LIVING ADJUSTMENT ("COLA"). The Service Fees set forth
                  in Section 2.1 for Access Line Charges (excluding that
                  component which is attributable to equipment), in Section 2.4
                  for Additional Network Charges (excluding the monthly charges
                  for Transport Services), in Section 2.5 for PASP Services, in
                  Section 5 for Application Support and Development Variable
                  Staff and in Section 6 for Output Processing Services may be
                  increased (but not decreased) for COLA during the Term
                  (including the transition period), in the amounts and on the
                  dates specified in the applicable sections below."

6.       The following new Section 8.7 shall be added to Exhibit E to the
         Agreement:

         "8.7     COLA ON PASP SERVICES.

                  (a)      INDEX. The parties agree to use the CPI-U for
                           purposes of determining the annual COLA adjustment
                           for Service Fees for PASP Services set forth in
                           Section 2.5. The base year index for CPI-U for
                           calculating COLA on the Service Fees for PASP
                           Services shall be the respective index on October 31,
                           2000 ("PASP Base Year Index").

                  (b)      CALCULATION. Beginning January 1, 2002, ALLTEL will
                           calculate and begin invoicing Client for the COLA
                           increases on the Service Fees for

                                        2
<PAGE>

                           PASP Services. The increase for COLA in a given year
                           will be onehundred percent (100%) of the increase in
                           the CPI-U calculated on the increase from the PASP
                           Base Year Index through the October 31 previous to
                           the January of the calculation:

7.       All capitalized terms not otherwise defined in this Third Amendment
         shall have the same meaning set forth in the Agreement.

8.       Except as herein expressly amended, the Agreement as previously amended
         is ratified, confirmed and remains in full force and effect.

9.       All references to the Agreement shall mean as such Agreement is amended
         hereby and as may in the future be amended, restated, supplemented or
         modified from time to time.

10.      This Third Amendment may be executed by the parties hereto individually
         or in combination, in one or more counterparts, each of which shall be
         an original and all of which shall constitute one and the same
         agreement.

         IN WITNESS WHEREOF, the parties have executed this Third Amendment as
of the Third Amendment Effective Date by their duly authorized representatives.

ALLTEL INFORMATION SERVICES, INC.          VALOR TELECOMMUNICATIONS
                                           ENTERPRISES, LLC

By:     Unsigned                           By:   /s/ Kenneth R. Cole
       -----------------------------             ---------------------------
Name:                                      Name: /s/ Kenneth R. Cole
       -----------------------------             ---------------------------
Title:                                     Title: /s/ President
       -----------------------------             ---------------------------

                                        3