<PAGE>
                                                                 EXHIBIT 10.29


                                                AMENDMENT #4 TO MASTER AGREEMENT

                                    FOR VALUE ADDED SERVICES (BRAZIL) BY BETWEEN
     AOL BRASIL LTDA, AND EMPRESA BRASILEIRA DE TELECOMUNICACOES S.A. - EMBRATEL

         This Amendment (the "Amendment #4"), effective as of April 25, 2001
(Amendment Date"), is entered into by and between AOL BRASIL LTDA., a Brazilian
corporation headquartered at Avenida Industrial 600, 2o. Andar, Santo Andre,
08090-500, Sao Paulo - SP, registered with the Ministerio de Fazenda under
number 03.032.579/0001-62, represented by its Director, Milton da Rocha Camargo,
hereinafter called AOL, and EMPRESA BRASILEIRA DE TELECOMUNICACOES S.A. -
EMBRATEL, a Brazilian corporation headquartered at Av. Presidente Vargas, 1012,
20179-900, Rio de Janeiro - RJ, registered with the Ministerio de Fazenda under
number 33.530,486/0001-29, represented by its Regional Sales Director, Sergio
Guedelha Coutinho, and its Account Manager, Marcus Viniclus Leme Brisola
Caseiro, hereinafter called EMBRATEL, and modifies, and is incorporated into,
the Master Agreement for Value Added Services (Brazil) dated October 18, 1999 by
and between AOL and EMBRATEL (the "Agreement").

         This Amendment modifies the section of the Agreement as indicated
below. Unless modified herein, all other terms defined in the Agreement shall
have the same meaning when used in this Amendment.

         All terms and conditions of the Agreement not otherwise specifically
modified in this Amendment remain unchanged and in full force and effect.

         In the case of conflict between the terms of this Amendment and the
remaining terms and conditions of the Agreement, the terms of this Amendment
shall control.

1.       DEPLOYMENT PLAN

         1.1 Exhibit C of the Agreement is hereby amended by ADDING the
following provisions, which shall terminate three (3) years after the effective
date of this Amendment:

         ---------- -------------------------------------- -------------------
                    AOL DESIGNATED CITIES                        MODEMS
         ---------- -------------------------------------- -------------------
            1.      BELEM - SP                                   [ ** ]
         ---------- -------------------------------------- -------------------
            2.      BELO HIROZONTE - MG                          [ ** ]
         ---------- -------------------------------------- -------------------
            3.      CURITIBA - PR                                [ ** ]
         ---------- -------------------------------------- -------------------
            4.      FLORIANOPOLIS - SC                           [ ** ]
         ---------- -------------------------------------- -------------------
            5.      FORTALEZA - CE                               [ ** ]
         ---------- -------------------------------------- -------------------
            6.      GOIANIA - GO                                 [ ** ]
         ---------- -------------------------------------- -------------------
            7.      LAGES - SC                                   [ ** ]
         ---------- -------------------------------------- -------------------
            8.      PETROPOLIS - RJ                              [ ** ]
         ---------- -------------------------------------- -------------------
            9.      PORTO VELHO - RO                             [ ** ]
         ---------- -------------------------------------- -------------------
            10.     RECIFE - PE                                  [ ** ]
         ---------- -------------------------------------- -------------------
            11.     SANTA MARIA - RS                             [ ** ]
         ---------- -------------------------------------- -------------------
            12.     UBERABA - MG                                 [ ** ]
         ---------- -------------------------------------- -------------------
                                               TOTAL             [ ** ]
         ---------- -------------------------------------- -------------------


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         1.2 Exhibit C of the Agreement is hereby amended by REDUCING the
following provisions, after the effective date of this Amendment:

          ---------- ------------------------------------- -------------------
                     AOL DESIGNATED CITIES                       MODEMS
          ---------- ------------------------------------- -------------------
             1.      JUNDIAI - SP                                [ ** ]
          ---------- ------------------------------------- -------------------
             2.      OSASCO - SP                                 [ ** ]
          ---------- ------------------------------------- -------------------
             3.      SANTO ANDRE - SP                            [ ** ]
          ---------- ------------------------------------- -------------------
                                                TOTAL            [ ** ]
          ---------- ------------------------------------- -------------------





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IN WITNESS WHEREOF, the parties hereto have executed this Amendment effective as
of the Amendment Date.

                                                       Sao Paulo, April 25, 2001

EMPRESA BRAS.                                        AOL BRASIL LTDA.
TELECOMUNICACOES S/A/ -
EMBRATEL

By:                                                  By:



/s/ SERGIO GUEDELHA COUTINHO                         /s/ MILTON CAMARGO
-----------------------------------------            --------------------------
Sergio Guedelha Coutinho                             Milton Camargo
SALES DIRECTOR                                       DIRECTOR

By:



/s/ MARCUS VINICIUS LEME BRISOLA CASEIRO
-----------------------------------------
Marcus Vinicius Leme Brisola Caseiro
ACCOUNT MANAGER

WITNESSES:

By:                                                  By:
   -----------------------------------                 ------------------------




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