<PAGE>


                                                                   EXHIBIT 10.19


                     MODIFICATION AND RATIFICATION OF LEASE


THE STATE OF TEXAS  Section
                    Section
COUNTY OF HARRIS    Section

     This is a Modification and Ratification of Lease ("Agreement") is made and
entered into as of the dates set forth on the signature page hereof, to be
effective as of the 1st day of September, 1997 (the "Effective Date"), between
RIGGS BANK, N.A., AS TRUSTEE OF THE MULTI-EMPLOYER PROPERTY TRUST ("Lessor"),
and U.S. LONG DISTANCE, INC., hereinafter referred to as Lessee ("Lessee").  For
and in consideration of Ten and No/100 Dollars ($10.00) and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto hereby agree as follows:

                              W I T N E S S E T H:

     WHEREAS, Lessor and Lessee hereby confirm, ratify and renew, except as
modified below, all of the terms, conditions and covenants in that certain
written Lease Agreement (the "Lease"), dated on or about November 10, 1992,
having a Commencement Date of September 1, 1992, between Lessor and Lessee for
the rental of the following described premises (the "Premises"):

          Approximately 6.814 rentable square feet of space identified as
          Suite(s) 200 & B100 located at 1001 TEXAS AVENUE, HOUSTON, TEXAS 77002
          (the "Building"), which lease space is depicted on Exhibit "1"
          attached to the Lease and incorporated herein by this reference.

All capitalized terms used herein which are not otherwise defined herein shall
have the meaning given such terms in the Lease.

     WHEREAS, the parties hereto desire to ratify, amend and renew the Lease and
further desire to reduce to writing their agreements regarding such matters.

     NOW, THEREFORE, for the consideration above stated, the parties hereto
hereby agree as follows:

     1.  CONFIRMATION, RATIFICATION AND RENEWAL OF LEASE.  Lessor and Lessee
hereby confirm, ratify and renew, except as modified herein, all of the terms,
conditions and covenants of the Lease.

<PAGE>

     2.   AMENDMENT OF RENT AMOUNT.  Pursuant to the first renewal option 
granted to Lessee in Paragraph 1 of the Additional Provisions attached to the 
Lease, effective September 1, 1997, the Lease is renewed and extended for an 
additional term of five (5) years ending August 31, 2002.  During the Renewal 
term, Lessee shall pay to Lessor the sum of $82,313.12 per year (which 
amounts to $6,859.43 per month) and being equivalent to $12.08 per square 
foot of Lessee's Net Rentable Area ("NRA") per year, plus additional rentals, 
if any, representing Lessee's pro rata share of actual building operating 
costs, as explained in paragraph 31.1 of the Lease, collectively referred to 
as "Base Rentals." It is agreed by both parties that the current market 
rental rate, as referenced in the renewal option clause of the Additional 
Provisions exhibit to the Lease, shall be the amount of $12.08 per square 
foot of NRA, and neither party shall have any right under any clause of the 
Lease to have the Base Rental rate redetermined by any court or other third 
party under any circumstance.

     3.   RENEWAL OPTION.  This Agreement represents the Lessee's exercise of
its first of two renewal options.  The renewal option, paragraph 1 of the
Additional Provisions (Exhibit 7) to the Lease, is hereby modified by deleting
the existing paragraph 1 and replacing it with the following:

          "1.  Lessee has the option to renew this lease agreement for one
          additional five (5) year period, commencing September 1, 2002, and
          ending August 31, 2007, at the then current market rental rate and
          terms, by giving written notice of renewal to Lessor at least thirty
          (30) days prior to the expiration of the term as then existing.  "

     4.   SUCCESSORS AND ASSIGNS.  This Agreement shall be binding upon, and
inure to the benefit of, the parties hereto, their respective successors and
permitted assigns.

     5.   LIMITED MODIFICATION.  Except as modified in this Agreement, the Lease
is and shall remain in full force and effect in accordance with its terms.

     6.   SEVERABILITY.  In the event any provision of this Agreement is held to
be invalid or unenforceable by final judgment of any court of competent
jurisdiction, then the invalidity or unenforceability of such provision shall
not affect any of the remaining provisions hereof, all of which remaining
provisions shall be and remain in full force and effect to the maximum extent
allowed by law.

     7.   AUTHORITY.     Each party hereto, and the individual executing this
Agreement on behalf of such party, represents and warrants to the other party,
that such party and its individual signatory or representative has full power
and authority to execute and enter into this Agreement and to bind such party to
all of the terms hereof.

     8.   ENTIRE AGREEMENT.  This Agreement represents the entire understanding
and agreement of Lessor and Lessee with regard to the modification, ratification
and renewal of the Lease, and all other prior written or verbal proposals and
discussions (except the Lease), and any

<PAGE>

alleged representations, warranties or agreements, regarding the subject matter
hereof are hereby superseded and rendered null and void and neither party shall
rely thereon.


     IN WITNESS WHEREOF, the parties hereto have executed this Modification and
Renewal Agreement as of the dates set forth below, to be effective as of the
Effective Date.

                              LESSOR:

                              RIGGS BANK, N.A., TRUSTEE OF THE
                              MULTI-EMPLOYER PROPERTY TRUST


                              By:   /s/ DAVID DONELSON
                                  --------------------------

                              Print Name:   David Donelson

                              Title:   Managing Director

                              Dated:  9/17, 1997


                              LESSEE:

                              U.S. LONG DISTANCE, INC.


                              By:   /s/ AUDIE LONG
                                  -------------------------------

                              Print Name:   Audie Long

                              Title:   Senior VP

                              Dated: