<PAGE>

                                                                     EXHIBIT 4.8

                  FIRST AMENDMENT (this "Amendment") to the SECOND AMENDMENT AND
            WAIVER dated as of April 28, 2003 (the "Second Amendment and
            Waiver"), to the Amended and Restated Credit Agreement dated as of
            July 25, 1997, as amended and restated as of March 29, 2001 (as
            heretofore amended, the "Credit Agreement"), among GRUPO IUSACELL
            CELULAR, S.A. de C.V., formerly known as Grupo Iusacell, S.A. de
            C.V. (the "Borrower"), the LENDERS party thereto (the "Lenders"),
            and JPMORGAN CHASE BANK, as Administrative Agent and Collateral
            Agent (the "Agent").

            WHEREAS the Borrower has requested that the Second Amendment and
Waiver be amended so as to extend the Termination Date (as defined in the Second
Amendment and Waiver) to June 13, 2003 in order to provide the Borrower and the
Parent with additional time to continue to work towards the formulation of a
consensual and comprehensive restructuring plan, and the undersigned Lenders,
constituting the Required Lenders, are willing to agree to such amendment on the
terms hereinafter set forth.

            NOW, THEREFORE, the parties hereto hereby agree as follows:

            1. Defined Terms. Capitalized terms used and not defined herein
shall have the meanings given to them in the Credit Agreement.

            2. Amendment. Effective as of the Amendment Effective Date (as
defined in Section 5), each reference in the Second Amendment and Waiver to "May
22, 2003" is hereby replaced with a reference to "June 13, 2003".

            3. Effect of Amendment. Except as expressly set forth herein, this
Amendment shall not by implication or otherwise limit, impair, constitute a
waiver of, or otherwise affect the rights or remedies of the Lenders or the
Agent under the Credit Agreement or any other Loan Document, and shall not
alter, modify, amend or in any way affect any of the terms, conditions,
obligations, covenants or agreements contained in the Credit Agreement or any
other Loan Document, all of which are ratified and affirmed in all respects and
shall continue in full force and effect. Nothing herein shall be deemed to
entitle the Borrower to a consent to, or a waiver, amendment, modification or
other change of, any of the terms, conditions, obligations, covenants or
agreements contained in the Credit Agreement or any other Loan Document in
similar or different circumstances. This Amendment shall apply and be effective
only with respect to the provisions of the Second Amendment and Waiver set forth
herein. After the date hereof, any reference to the Second Amendment and Waiver
shall mean the Second Amendment and Waiver as modified hereby, and any reference
to the Credit Agreement shall mean the Credit Agreement, as amended by the
Second Amendment and Waiver (as amended
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                                                                               2


hereby). This Amendment shall constitute a "Loan Document" for all purposes of
the Credit Agreement and the other Loan Documents.

            4. Representations and Warranties. The Borrower hereby represents
and warrants to the Agent and the Lenders as of the date hereof as follows:

            (a) After giving effect to the amendment set forth in Section 2, no
Default or Event of Default has occurred and is continuing.

            (b) The execution, delivery and performance by the Borrower of this
Amendment have been duly authorized by all necessary corporate and other action
and do not and will not require any registration with, consent or approval of,
notice to or action by, any person (including any governmental agency) in order
to be effective and enforceable. The Credit Agreement as amended and waived by
the Second Amendment and Waiver (as amended by this Amendment) constitutes the
legal, valid and binding obligation of the Borrower, enforceable against it in
accordance with its terms, subject to applicable bankruptcy, insolvency,
reorganization, moratorium or other laws affecting creditors' rights generally
and subject to general principles of equity, regardless of whether considered in
a proceeding in equity or at law.

            (c) The officers of the Borrower executing this Amendment have the
authority to do so, as evidenced by a notarized power of attorney delivered on
the date hereof to the Agent and satisfactory to the Agent.

            5. Effectiveness. This Amendment shall become effective (the
"Amendment Effective Date") when (a) the Agent shall have received (i)
counterparts hereof duly executed and delivered by the Borrower and the Required
Lenders and (ii) the notarized power of attorney referred to in Section 4(c) and
(b) the Borrower shall have paid all amounts due and payable under the Credit
Agreement and not yet paid, including all out-of-pocket expenses of the Agent
(including fees and disbursements of Mexican and United States counsel) for
which invoices have been submitted.

            6. Expenses. The Borrower agrees to reimburse the Agent for its
reasonable and documented out-of-pocket expenses in connection with this
Amendment, including the reasonable and documented fees, charges and
disbursements of Cravath, Swaine & Moore LLP, United States counsel for the
Agent and Ritch, Heather y Mueller, S.C., Mexican counsel for the Agent, and
Alvarez & Marsal, Inc., financial advisor to the Lenders.

            7. GOVERNING LAW; COUNTERPARTS. (a) THIS AMENDMENT AND THE RIGHTS
AND OBLIGATIONS OF THE PARTIES HERETO SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO CONFLICT OF
LAW PRINCIPLES.

            (b) This Amendment may be executed in any number of counterparts and
by different parties hereto on separate counterparts, each of which when so
executed and delivered shall be deemed an original, but all of which together
shall constitute a single
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                                                                               3


instrument. Delivery of an executed counterpart of a signature page of this
Amendment by facsimile transmission shall be as effective as delivery of a
manually executed counterpart hereof.

            8. Submission to Jurisdiction. (a) Each of the parties hereto hereby
irrevocably and unconditionally submits to the jurisdiction of the Supreme Court
of the State of New York sitting in New York County and of the United States
District Court of the Southern District of New York, and any appellate court
from any thereof, and to the courts of its own corporate domicile in respect of
actions brought against it as a defendant in any action or proceeding arising
out of or relating to any Loan Document, or for recognition or enforcement of
any judgment, and each of the parties hereto hereby irrevocably and
unconditionally agrees that all claims in respect of any such action or
proceeding may be heard and determined in such court. Each of the parties hereto
agrees that a final judgment in any such action or proceeding shall be
conclusive and may be enforced in other jurisdictions by suit on the judgment or
in any other manner provided by law.

            (b) The Borrower hereby irrevocably and unconditionally waives, to
the fullest extent it may legally and effectively do so, any objection which it
may now or hereafter have to the laying of venue of any suit, action or
proceeding arising out of or relating to this Amendment in any court referred to
in paragraph (a) of this Section. Each of the parties hereto hereby irrevocably
waives, to the fullest extent permitted by law, the defense of an inconvenient
forum to the maintenance of such action or proceeding in any such court and any
right to which it may be entitled on account of place of residence or domicile.

            (c) The Borrower hereby irrevocably designates, appoints and
empowers CT Corporation as its process agent to receive for and on its behalf
service of process in New York in any legal action or proceeding with respect to
any Loan Document. It is understood that a copy of any such process served on
such process agent shall be promptly forwarded by air mail by the person
commencing such proceeding to the Borrower at its address specified in the
Credit Agreement, but the failure of the Borrower to receive such copy shall not
affect in any way the service of such process as aforesaid.

            (d) Each party to this Amendment irrevocably consents to service of
process in the manner provided for notices in the Credit Agreement. Nothing in
this Amendment will affect the right of any party to this Amendment to serve
process in any other manner permitted by law.
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                                                                               4


            IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly executed and delivered by their respective proper and duly authorized
officers as of the day and year first above written.

                                        GRUPO IUSACELL CELULAR, S.A. de C.V.,

                                          by /s/ Carlos Espinal G.
                                            ----------------------
                                             Name: Carlos Espinal G.
                                             Title: [illegible]

                                          by /s/ Russell A. Olson
                                            ----------------------

                                             Name: Russell A. Olson
                                             Title: [illegible]


                                        JPMORGAN CHASE BANK, individually and as
                                        Administrative Agent,

                                          by [illegible signature]
                                            ----------------------
                                              Name: [illegible]
                                              Title: [illegible]
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                                                                               5

                                                               SIGNATURE PAGE to
                                     FIRST AMENDMENT dated as of May 22, 2003 to
                                                     SECOND AMENDMENT AND WAIVER
                                         to GRUPO IUSACELL CELULAR, S.A. DE C.V.
                                           AMENDED AND RESTATED CREDIT AGREEMENT


                        To approve the First Amendment to the Second Amendment
                        and Waiver:

                        Name of Institution: JP MORGAN CHASE BANK

                                                  by  /s/ Manochere Alamgir
                                                      --------------------------
                                                      Name: Manochere Alamgir
                                                      Title: Vice President
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                                                                               5

                                                               SIGNATURE PAGE to
                                     FIRST AMENDMENT dated as of May 22, 2003 to
                                                     SECOND AMENDMENT AND WAIVER
                                         to GRUPO IUSACELL CELULAR, S.A. DE C.V.
                                           AMENDED AND RESTATED CREDIT AGREEMENT


                        To approve the First Amendment to the Second Amendment
                        and Waiver:

                        Name of Institution: Bank of Boston Fleet National Bank

                                                  by  /s/ Fred P. Lucy, II
                                                      --------------------------
                                                      Name: Fred P. Lucy, II
                                                      Title: Vice President
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                                                                               5

                                                               SIGNATURE PAGE to
                                     FIRST AMENDMENT dated as of May 22, 2003 to
                                                     SECOND AMENDMENT AND WAIVER
                                         to GRUPO IUSACELL CELULAR, S.A. DE C.V.
                                           AMENDED AND RESTATED CREDIT AGREEMENT


                        To approve the First Amendment to the Second Amendment
                        and Waiver:

                        Name of Institution: Australia and New Zealand Banking
                                             Group Limited

                                                  by  /s/ Brian M. Foster
                                                      --------------------------
                                                      Name: Brian M. Foster
                                                      Title: Associate Director
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                                                                               5

                                                               SIGNATURE PAGE to
                                     FIRST AMENDMENT dated as of May 22, 2003 to
                                                     SECOND AMENDMENT AND WAIVER
                                         to GRUPO IUSACELL CELULAR, S.A. DE C.V.
                                           AMENDED AND RESTATED CREDIT AGREEMENT


                        To approve the First Amendment to the Second Amendment
                        and Waiver:


                        Name of Institution: BNP Paribas

                                                  by  /s/ Curt Deane
                                                      --------------------------
                                                      Name: Curt Deane
                                                      Title: Director
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                                                                               5

                                                               SIGNATURE PAGE to
                                     FIRST AMENDMENT dated as of May 22, 2003 to
                                                     SECOND AMENDMENT AND WAIVER
                                         to GRUPO IUSACELL CELULAR, S.A. DE C.V.
                                           AMENDED AND RESTATED CREDIT AGREEMENT


                        To approve the First Amendment to the Second Amendment
                        and Waiver:


                        Name of Institution: The Toronto-Dominion Bank

                                                  by  /s/ Jill Hall
                                                      --------------------------
                                                      Name: Jill Hall
                                                      Title: Mngr. Credit Admin.
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                                                                               5

                                                               SIGNATURE PAGE to
                                     FIRST AMENDMENT dated as of May 22, 2003 to
                                                     SECOND AMENDMENT AND WAIVER
                                         to GRUPO IUSACELL CELULAR, S.A. DE C.V.
                                           AMENDED AND RESTATED CREDIT AGREEMENT






                        To approve the First Amendment to the Second Amendment
                        and Waiver:


                        Name of Institution: CITIBANK, N.A.

                                                  by  /s/ Randolph Thornton
                                                      --------------------------
                                                      Name: Randolph Thornton
                                                      Title: Managing Director
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                                                                               5

                                                               SIGNATURE PAGE to
                                     FIRST AMENDMENT dated as of May 22, 2003 to
                                                     SECOND AMENDMENT AND WAIVER
                                         to GRUPO IUSACELL CELULAR, S.A. DE C.V.
                                           AMENDED AND RESTATED CREDIT AGREEMENT


                        To approve the First Amendment to the Second Amendment
                        and Waiver:


                        Name of Institution: Bank of America N.A.

                                                  by  /s/ James P. Garvey
                                                      --------------------------
                                                      Name: James P. Garvey
                                                      Title: Principal