<PAGE>   1
                                                                    Exhibit 10.3

                         CELLULAR MOBILE RADIOTELEPHONY

                                REGION 6 "CENTER"


                               TITLE OF CONCESSION

The Federal Government, through the Ministry of Communications and
Transportation, represented herein by its Minister, ANDRES CASO LOMBARDO, hereby
grants this Title of Concession to SISTEMAS TELEFONICOS PORTATILES CELULARES,
S.A. DE C.V., which for the purpose of this Title shall be referred to,
respectively as the MINISTRY and the receiver of the Concession ("GRANTEE"), in
accordance with the following antecedents and conditions.


                                   ANTECEDENTS

         I. The 1989-1994 Plan Nacional de Desarrollo (National Development
         Plan) sets forth the importance of updating and improving
         telecommunications as a mean for the development of the nation and
         underlines the need to diversify services, improve their quality and
         expand their coverage with greater participation by private entities.

         II. The technological improvement in switching equipment and cellular
         radiocommunication systems makes it possible to use more efficiently
         the redioelectrical spectrum to serve a larger number of users with
         radiotelephony of improved quality and at a lower cost.

         III. On January 17,1990, Sistemas Telefonicos Portatiles Celulares,
         S.A. de C.V., filed an application with the Ministry of Communications
         and Transportation for a concession to install, operate and
         commercially exploit a mobile radiotelephony public service network
         with cellular technology in Region 6 "Center".

         IV. In accordance with the provisions of Article 15 of the Ley
         Generales de Vias de Comunicacion [Law on General Means of
         Communication (hereinafter the "Communications Law")], the MINISTRY
         processed the application for the concession, and, in due course,
         ordered its publication in the Official Gazette and in one of the
         newspapers of widest circulation in the region, which were made on
         April 19 and May 4, 1990. The objections raised to said application
         were rejected by the MINISTRY based on the report of the Advisory
         Technical Commission of General Means of Communication. In the report
         it was determined that the objections raised lacked founded grounds.

         V. In accordance with the above-mentioned antecedents and based on the
         fact that Sistemas Telef6nicos Portbtiles Celulares, S.A. de C.V., met
         the technical, legal and financial requirements, the Federal
         Government, through the MINISTRY, based on the provisions of Article 36
         of the Organic Law of the Federal Public Administration, and Articles,
         1st, 2nd, 3rd, 8th, 14th, 15th and other related provisions of the Law
         on Communications and Article 4th of its Internal Regulation, grants
         the following




                                                                               1
<PAGE>   2
                                   CONCESSION

To build, install, maintain, operate and commercially exploit for a term of 20
years a public radiotelephony network with cellular technology in the assigned
frequency band of 825-835/870-880 MHz., for Region 6 "Center", comprising the
States of Aguascalientes, San Luis Potosi, Zacatecas, Guanajuato, Queretaro, and
the municipalities of Huejucar, Santa Maria de los Angeles, Colotlan,
Teocaltiche, Huejuquilla, Mesquitic, Villa Guerrero, Bolanos, Lagos de Moreno,
Villa Hidalgo, Ojuelos y Encarnacion de Diaz of the State of Jalisco.

GRANTEE, through the concessioned mobile public radiotelephony network must
provide the subscribers with mobile public radiotelephony service,
interconnected to the basic telephone network concessioned to Telefonos de
Mexico, S.A. de C.V., and to other networks authorized by the MINISTRY.

GRANTEE accepts this concession in accordance with the terms set forth in the
conditions of the eight chapters of this concession, which shall become
effective on the date of its execution.

                                                      Mexico City, July 23, 1990



     MINISTER OF COMMUNICATIONS                 SISTEMAS TELEFONICOS PORTATILES

         AND TRANSPORTATION                         CELULARES, S.A. DE C.V.


              (SIGNED)                                      (SIGNED)


        ANDRES CASO LOMBARDO                       GABRIEL ALARCON VELAZQUEZ




                                                                               2
<PAGE>   3
                                   CONDITIONS

                                   CHAPTER 1

                     DEFINITIONS AND SCOPE OF THE CONCESSION

1.1.     MOBILE PUBLIC RADIOTELEPHONY NETWORK WITH CELLULAR TECHNOLOGY

         The mobile public radiotelephony network with cellular technology
         referred to in this concession, hereinafter the "NETWORK", consists of
         cellular switch exchanges, base radioelectrical stations, links between
         this exchanges and stations and other facilities and equipment directly
         involved in the service of transmitting voice and data signals between
         subscribers of the NETWORK through channels and circuits of
         radioelectrical frequencies, as well as their interconnection to the
         basic public telephony network concessioned to Telefonos de Mexico,
         S.A. do C.V. (hereinafter referred to as "Basic Public Telephony
         Network") and other public telecommunication networks.

         The subscribers' mobile or fixed radiotelecommunication terminal
         equipment does not form part of the NETWORK.

         GRANTEE must operate the NETWORK in the frequencies of cellular group
         "A", which is formed of 333 pairs of frequencies in bands of
         825-835/870-880 MHz., with 30 KHz., of spacing between channels, as
         mentioned in Schedule "B" hereof. Said frequency bands may not be
         modified without the prior authorization from the MINISTRY.

         The concessioned service area is formed by Region 6 "Center",
         comprising the States of Aguascalientes, San Luis Potosi, Zacatecas,
         Guanajuato, Queretaro, and the municipalities of Huejucar, Santa Maria
         de los Angeles, Colotian, Teocaltiche, Huejuquilla, Mesquitic, Villa
         Guerrero, Bolanos, Lagos de Moreno, Villa Hidalgo, Ojuelos y
         Encarnacion de Diaz of the State of Jalisco.

1.2.     MOBILE CELLULAR RADIOTELEPHONY SERVICE

         The cellular mobile radiotelephony service that the GRANTEE is hereby
         obliged to provide, is a final telecommunication service whereby
         complete capacity is supplied for voice transmission between
         subscribers, as well as its interconnection with the users of the basic
         public telephony network and other authorized public telecommunications
         networks.

         GRANTEE, in order to provide a complete public radiotelephony service
         agrees to:

                  a) Install, maintain and operate the network to allow the
                  transmission of signals between the terminal radiotelephony
                  equipment of the subscribers, as well as its interconnection
                  with the basic telephony network and other telecommunication
                  networks authorized by the MINISTRY.



                                                                               3
<PAGE>   4
                  b) At the request of the subscribers, supply, connect and
                  maintain the terminal radiotelephony equipment.

                  The subscriber may acquire the terminal equipment from another
                  independent competing company and the GRANTEE shall be
                  obliged, in order to provide the service of transmission of
                  signals, to connect said equipment to the NETWORK. GRANTEE
                  shall not be obliged to provide maintenance service to
                  terminal equipment of those subscribers that acquire it from
                  another company.

                  c) Provide long distance telephone service to its subscribers,
                  through the interconnection with the basic telephony public
                  network and other long distance networks authorized by the
                  MINISTRY.

                  d) Provide public radiotelephony booths service, which are
                  terminal equipment that forms part of the NETWORK and which
                  shall be available to the public.

1.3.     MARKETING, INSTALLATION AND MAINTENANCE OF TERMINAL EQUIPMENT

         The marketing, installation and maintenance of the terminal
         radiocommunication equipment for the public, shall be handled by the
         GRANTEE through a separate accounting, by one of its affiliates,
         subsidiaries or commercial agents.

         In the rendition of the concessioned services, the GRANTEE shall be
         directly liable to the MINISTRY and the users. The standard agreements
         with the commercial agents must be authorized by the MINISTRY prior to
         its execution.

1.4.     COMPLEMENT AND VALUE ADDED SERVICES

         GRANTEE shall require a permit from the MINISTRY to provide special and
         complement telecommunication and value added or teleinformation
         services.

         If applicable, the GRANTEE shall provide this services on a competitive
         basis by maintaining a separate account or thorough its affiliates or
         subsidiaries, when so determined by the MINISTRY.



                                                                               4
<PAGE>   5
                                   CHAPTER 2

                               GENERAL PROVISIONS

2.1.     APPLICABLE LAWS

         The public service subject matter of this concession is governed by the
         Mexican Constitution, the Law on Communications and the Ley General de
         Bienes Nacionales (General Law on National Assets) and its regulations;
         by the international treaties and conventions executed and ratified by
         the Mexican government and that are in relation with this concession,
         and by the laws in force and the terms of this concession.

2.2.     MAJORITY CONTROL OF SHARE CERTIFICATES BY MEXICANS

         GRANTEE covenants and agrees that its capital and its board of
         directors shall be structured in such a way that the authority to
         control and manage the corporation shall always rest with Mexican
         shareholders.

         Foreign investment may not exceed 49% of the total shares representing
         the capital stock.

2.3.     AMENDMENTS TO THE BY-LAWS

         GRANTEE covenants and agrees to submit to the approval of the MINISTRY
         any amendments to its deed of incorporation, by-laws, capital
         increases, composition of its capital stock and regulations in
         connection with its dealings or relations with the public, prior to its
         execution.

2.4.     RIGHTS IN REM AND COMPETITION

         This concession does not create rights in rem in favor of the GRANTEE
         or third parties in regard to the assets of national domain destined to
         the concessioned services. Therefore, any monopoly practice by the
         GRANTEE regarding said assets shall give rise to the early termination
         of this concession.

         The MINISTRY reserves the right to grant other concession or
         concessions in favor of third parties to commercially exploit, within
         the same geographical area or in an other area, services identical or
         similar to those that are subject matter of this concession,

         The MINISTRY may grant concessions or permits for the establishment of
         telecommunication services that compete with those of the GRANTEE. To
         grant other concessions, the MINISTRY shall take into account the
         efficiency of the public service subject matter of this concession, the
         financial stability of the GRANTEE and fair competition.



                                                                               5
<PAGE>   6
2.5.     ASSIGNMENT OF RIGHTS

         GRANTEE may not assign, transfer, or dispose in any manner whatsoever,
         totally or partially, of this concession or the rights derived
         therefrom, without the prior approval from the MINISTRY.

         If the MINISTRY grants its consent, the respective agreement or
         contract shall be subject to the applicable laws and regulations.

         The assets specified in Article 192 of the Communications Law, with the
         exception of the band of the assigned radioelectrical spectrum, may be
         mortgaged or encumbered.

2.6.     PROHIBITION TO ASSIGN RIGHTS TO FOREIGN GOVERNMENTS OR STATES

         In no event may the GRANTEE, directly or indirectly, assign, mortgage
         or in any manner encumber or dispose of this concession, the rights
         granted herein, the works and installations, shares certificates,
         issued debentures or bonds, to any foreign government or state or admit
         them as partners or associates. Any transaction carried out in
         violation of this provision shall be null and void.

         Furthermore, if a foreign government acquires shares, debentures or
         bonds issued by the GRANTEE, the same shall become null and void as of
         the date of such acquisition.

         Mexican companies which are shareholders of the GRANTEE may have, as
         minority shareholders, foreign state-owned companies, provided said
         foreign companies agree to be considered as Mexicans in regard to the
         titles they may acquire, not to request or accept the intervention of
         the government of their country of origin or of any other country, and
         of international organizations, weather public or private, under the
         penalty to forfeit all the assets or rights they may have acquired for
         the benefit of the Mexican Nation.

2.7.     RESTRICTIONS OF THE POWERS OF ATTORNEY

         GRANTEE may in no event grant general irrevocable powers-of-attorney
         for lawsuits and collections, acts of administration or acts of domain
         in favor of companies that, directly or indirectly, result in the
         displacement of the rights and obligations of the GRANTEE established
         in this concession.

2.8.     PROHIBITION TO RESORT TO FOREIGN INTERVENTION

         GRANTEE has evidenced to the MINISTRY that it is incorporated in
         accordance with the laws of the Mexican Republic and that therefore, it
         shall not have, in connection with the validity, construction or
         execution of this concession, other rights and remedies than those
         granted by the Mexican laws to Mexican nationals. Accordingly, GRANTEE
         covenants and agrees not to request or accept in connection with the
         services referred in this concession, the diplomatic intervention of
         any public or private international organization, under the penalty of
         forfeiting for the benefit of the Mexican Nation, all assets and rights
         it may


                                                                               6
<PAGE>   7
         have acquired to construct, create and commercially exploit the
         communication means and the concessioned services.

2.9.     ANTITRUST

         In no event shall GRANTEE use unlawful restrains to hinder fair
         competition in those activities where GRANTEE is directly involved or
         on those that it conducts through its subsidiaries.

         GRANTEE is prohibited from carrying out or executing acts, agreements,
         contracts or combinations thereof with the intent of obtaining an
         unlawful exclusive advantage in its favor or in favor of other persons,
         or that is aimed to create a monopoly on the market of other
         complemental services.

2.10.    PROHIBITION OF CROSS-SUBSIDIES AND PREFERENTIAL TREATMENT

         GRANTEE may not receive from or grant subsidies to any other of the
         grantees of telecommunication services or preferential treatment.
         GRANTEE must inform the MINISTRY of the steps taken to settle
         complaints filed by its clients or by other companies that compete with
         the GRANTEE regarding violations of this provisions.






                                                                               7
<PAGE>   8
                                   CHAPTER 3

                          NETWORK EXPANSION AND UPDATE

3.1.     EXPANSION PROGRAM

         GRANTEE agrees to prepare and submit each year to the MINISTRY its
         five-year program, outlining and detailing, the quality, coverage and
         update objectives for the first two years. In order to maintain the
         consistency of this program with the National Development Plan and with
         the Regional Telecommunication Program, GRANTEE shall discuss said
         program with the MINISTRY. GRANTEE shall inform annually to the
         MINISTRY its compliance with the referred program.

         GRANTEE agrees to install the NETWORK with a minimum capacity to serve:

         -- In the first year, 8,500 users in 12 towns

         -- In the fifth year, 27,000 users in 20 towns


         At the end of the fifth year of this concession, the NETWORK must have
         a territorial coverage of Region 6 "Center", serving those cities and
         towns where at least 75% of the population lives.

         GRANTEE agrees to comply with the quality standards approved by the
         MINISTRY.

         When GRANTEE installs the equipment to be used in the operation of the
         NETWORK, it shall take into account the safety and convenience of the
         public, of its assets and of other public services, as. to not
         interfere with the normal performance thereof.

3.2.     NETWORK LINKS

         GRANTEE may install and operate the transmission and switching
         infrastructure it may require to transmit communication, control and
         supervision signals between its cellular switch exchanges and the base
         radioelectrical stations and of interconnection with other networks or,
         else, it may use the networks of other companies or entities authorized
         by the MINISTRY to provide said services to third parties.

3.3.     RURAL RADIOTELEPHONY

         GRANTEE agrees to expand NETWORK coverage in order to cover rural areas
         in accordance with the programs it may agree upon with the MINISTRY
         every five years.



                                                                               8
<PAGE>   9
3.4.     PUBLIC RADIOTELEPHONY BOOTHS

         GRANTEE agrees to install and maintain in operation radiotelephony
         public booths in its service area, in accordance with the expansion
         program it may have agreed upon with the MINISTRY every five years.
         GRANTEE shall discuss, from time to time, with the MINISTRY, the
         guidelines to determine where the new public radiotelephony booths must
         be installed.

3.5.     TECHNICAL PLANS AND STANDARDS

         GRANTEE agrees to comply with the technical standards indicated by the
         MINISTRY and to submit to the MINISTRY's consideration the plans for
         the numbering, signaling, transmission, switching, synchronization and
         rate fixing, taking into account the needs of other public operators of
         telecommunications services interconnected with the NETWORK and those
         of its final users.

3.6.     APPROVAL OF EQUIPMENT

         GRANTEE agrees to install in its network, switching and transmission
         equipment that meets national standards and regulations applicable to
         public telecommunication networks, which must comply with the approval
         and registration standards established by the MINISTRY.

         In order to facilitate the fulfillment of the above-mentioned
         condition, the MINISTRY shall promote the establishment and efficient
         performance of Advisory Standardization Committees in those industries
         where the GRANTEE or its suppliers participate, as well as of testing
         laboratories.

3.7.     NETWORK MODIFICATIONS

         GRANTEE must obtain the authorization of the MINISTRY to carry out
         modifications to the NETWORK, when such modifications alter the
         functioning of telephones and of other networks interconnected thereto.

3.8.     UPDATING NETWORK

         GRANTEE agrees to update and digitize the NETWORK for the concessioned
         service by bringing about technological improvements that allow a
         better use of the frequencies allocated, as well as the improvement of
         the quality and productivity of the service.

3.9.     TECHNICAL AND INDUSTRIAL RESEARCH

         In coordination with the Mexican Institute on Communications and other
         research institutions, GRANTEE agrees to promote technical and
         industrial research in matters of mobile cellular radiotelephony and
         similar services.

         Under the terms determined by MINISTRY, GRANTEE agrees to assist in the
         updating of the infrastructure owned by the MINISTRY for the
         supervision and control of radioelectrical spectrum.



                                                                               9
<PAGE>   10
3.10.    TECHNOLOGICAL TRAINING AND EDUCATION

         GRANTEE shall develop training programs for its personnel in order to
         assist in its updating. In addition, in order to promote professional
         development of radiotelecommunications, GRANTEE shall establish support
         programs for technical education, which shall be coordinated with the
         leading Mexican education institutions.








                                                                              10
<PAGE>   11
                                   CHAPTER 4


                          SERVICE OPERATION AND QUALITY

4.1.     QUALITY OF SERVICE AND CONTINUITY

         GRANTEE agrees to provide the public service subject matter of this
         concession, in an efficient and continuous manner, meeting the quality
         and operation standards established by the MINISTRY.

         The concessioned network must be capable of serving the traffic calls
         of its subscribers with a 0.02 probability of blockage, in addition to
         achieving call connection time of less than 10 seconds in 80% of the
         cases, provided there are no obstacles beyond the control of the
         GRANTEE.

         GRANTEE agrees to establish quality measurement and control systems for
         the concessioned service. Said systems must be transparent, reliable
         and easily verifiable by the MINISTRY. At minimum, the system must
         include parameters related to the goals and quality standards that may
         be established.

4.2.     EQUAL TREATMENT

         In the rendition of the services subject matter of this concession,
         GRANTEE shall refrain from granting privileges or making distinctions
         in favor of or against certain individuals or corporations.

4.3.     CONFIDENTIALITY OF SERVICE

         In the rendition of the concessioned services, GRANTEE must guarantee
         the confidentiality of the information of the users of the service and
         of those generated through the public concessioned network and not to
         disclose it unless prior authorization to that effect is obtained.

4.4.     TELEPHONE DIRECTORY

         GRANTEE must provide telephone consultation services to the directory
         in those cases where the users have requested specifically such
         service.

4.5.     COMPLAINT AND REPAIR SERVICE

         GRANTEE must establish an efficient system for the reception and
         processing of claims and NETWORK breakdowns, and shall monthly inform
         to the MINISTRY the volume of complaints presented, the results of the
         repair services and the application of discounts resulting from the
         interruption of the service and other compensations derived from
         noncompliance with the quality standards.

4.6.     QUALITY MEASUREMENT AND CONTROL EQUIPMENT

         GRANTEE agrees to publish every two years, upon prior agreement with
         the MINISTRY, a system of quality standards for the concessioned
         service, which shall be updated from time to time in accordance with
         international standards.


                                                                              11
<PAGE>   12
         Likewise, the system must set forth the compensation which the users
         shall be entitled to receive in the event GRANTEE fails to comply with
         the establish quality standards.

         GRANTEE must take all reasonable steps to guarantee the accuracy and
         reliability of any measuring device used in connection with the system
         for the purpose of quality measuring and invoicing. In addition,
         GRANTEE shall keep all records that the MINISTRY deems advisable in
         connection with any measuring device that the MINISTRY considers to be
         a source of problems.

         GRANTEE agrees to allow the MINISTRY to review and inspect the form in
         which any measuring device is used and agrees to allow the MINISTRY to
         conduct tests for the purpose of evaluating their accuracy, reliability
         and compliance with standards.

4.7.     SERVICE INTERRUPTION

         Whenever service is interrupted for more than 72 consecutive hours,
         GRANTEE shall grant to the users a discount of the applicable fees for
         all the time of the interruption of services, even in those cases where
         the suspension is due to acts of God or force majeure. The discount
         made to the users shall in no way affect MINISTRY's right to impose
         administrative sanctions.

4.8.     EMERGENCY SERVICES

         GRANTEE must prepare a plan which shall be agreed upon with the
         MINISTRY, to provide emergency services in cases where acts of God or
         force majeure cases may arise.

         GRANTEE agrees to provide emergency services within its concessioned
         area free of any charge. In addition, GRANTEE agrees to provide
         assistance services to emergency institutions and organizations, giving
         priority to their communications. GRANTEE shall provide the emergency,
         safety and assistance services in accordance with applicable
         international treaties.

4.9.     CODE OF COMMERCIAL PRACTICES

         Within the six months following the granting of the concession, GRANTEE
         must deliver to the users of the concessioned service, a code of
         commercial practices that regulates the relation an dealings of the
         GRANTEE with the users of the service. Said commercial code shall be
         previously submitted to the MINISTRY for its authorization. The code
         shall serve as a guide for the GRANTEE's clients and employees in
         connection with any dispute or complaint that may arise in the
         rendition of the services. The commercial code shall be reviewed by
         both the MINISTRY and the GRANTEE every three years.

4.10.    SERVICE AGREEMENT

         GRANTEE must execute a service agreement with all the users of the
         concessioned service. Said agreement shall establish the general
         conditions of the service and shall not contravene the conditions of
         this concession.



                                                                              12
<PAGE>   13
         GRANTEE must submit to the MINISTRY the standard service agreement for
         its approval.

4.11.    RESPONSIBILITY TOWARDS THE USERS

         GRANTEE shall be the sole responsible party in the rendition of the
         concessioned services. Consequently, the MINISTRY is released from any
         liability towards the users of the concessioned service. In the event
         GRANTEE does not provide the concessioned service in accordance with
         the terms and conditions stated in this concession, the MINISTRY shall
         have the right to take whatever measures it deems necessary.

4.12.    PROHIBITION TO CONDUCT CONDITIONED SALES

         Unless unavoidable technical conditions exit, GRANTEE shall refrain
         from forcing the users of the concessioned service to acquire other
         assets, services or securities as a condition to provide the service.

4.13.    PROHIBITION TO CONDITION PURCHASE OF EQUIPMENT

         GRANTEE shall refrain from making a condition to purchase materials,
         telecommunication equipment or services, that the supplier of such
         goods, equipment or services, covenants to sell exclusively the goods
         or services of the GRANTEE.






                                                                              13
<PAGE>   14
                                   CHAPTER 5

                                 INTERCONNECTION

5.1.     INTERCONNECTION WITH THE BASIC PUBLIC TELEPHONY NETWORK

         GRANTEE agrees to interconnect the NETWORK with the basic public
         telephony network concessioned to Telefonos de Mexico, S.A. de C.V.
         ("Telmex"). For such purpose, GRANTEE may execute an interconnection
         agreement, which shall include at minimum the following:

                  1) the method to be adopted to establish and maintain the
                  connection;

                  2) the connecting points of the NETWORK in which the
                  connection is to be made, including arrangements to determine
                  the point where the signals are to be transferred from one
                  telecommunication network to another and the arrangements to
                  transmit and route signals in case of an emergency;

                  3) the dates or period when the GRANTEE or Telmex agree to
                  carry out or permit that the interconnection arrangements are
                  carried out;

                  4) the necessary capacity to permit that the traffic of
                  signals between the NETWORK and the other networks may be of
                  reasonable quality;

                  5) the dates or periods that the GRANTEE or Telmex agree upon
                  to review the terms and conditions of the agreement;

                  6) the form on which the signals must be transmitted or
                  received at the terminal points of the NETWORK, including
                  numbering arrangements and signaling methods;

                  7) the procedure to guarantee that signals are received with a
                  quality that is consistent with the recommendations of the
                  International Union on Telecommunications, accepted by Mexico
                  or any other standard that from time to time may be accepted
                  by the MINISTRY;

                  8) the collection arrangements between GRANTEE and Telmex for
                  signals transmitted to third parties by virtue of
                  interconnection within or outside the Mexican Republic;

                  9) provisions for contingent obligations that any of the
                  parties may experience as a result of the interconnection.

                  10) the charges and rates that must be paid to Telmex by
                  GRANTEE; and

                  11) any other matter that the MINISTRY deems necessary.



                                                                              14
<PAGE>   15
         If after a term that at the sole discretion of the MINISTRY is
         reasonable, GRANTEE and Telmex have not reached an interconnection
         agreement, at the request of any of the parties, the MINISTRY shall
         determine the terms and conditions of those items to which the parties
         have not reached an agreement. To that effect, the following guidelines
         must be followed:

                  a) GRANTEE shall reimburse to Telmex the cost of establishing
                  and maintaining the interconnection, through an arrangement
                  which must include a complete allocation of costs attributable
                  to the services rendered;

                  b) that Telmex receives and indemnification for damages that
                  may be caused to the NETWORK resulting from the
                  interconnection and that GRANTEE maintains Telmex free from
                  all and any liabilities with third parties;

                  c) that the quality of all telecommunications services
                  rendered through the NETWORK and other interconnected networks
                  is maintained at all times;

                  d) that the requirements of fair competition are met;

                  e) that any other matter required for the protection of the
                  rights of Telmex and GRANTEE is fairly taken into account,
                  including the need to assure that;

                         -- the connection arrangements are consistent with
                         acceptable engineering principles and practices;

                         -- the GRANTEE is not obliged to unduly rely on the
                         services rendered by Telmex;

                         -- Telmex obligations with the GRANTEE are established
                         taking into account Telmex's obligation to create
                         connecting points for others;

                         -- where possible, the arrangements to be made under
                         this condition are similar to those with other
                         operators, without taking into account the diversity or
                         number of operators that may contract with Telmex in
                         accordance with this condition; and

                         -- the technical developments and numbering
                         arrangements of the NETWORK are not limited beyond what
                         is deem advisable;

                  f) That the costs of the interconnection and other services to
                  the GRANTEE reflect their cost of rendition and that said
                  costs are competitive in an international level.

         GRANTEE shall not be obliged to execute interconnection agreements with
         operators in any of the following events;



                                                                              15
<PAGE>   16
                  i) When, in the opinion of the GRANTEE, it may endanger life
                  or safety of human beings or cause death or damages to
                  persons, property or to the quality of any of the
                  telecommunication services rendered through the NETWORK,
                  provided that the MINISTRY has not expressed a contrary
                  opinion;

                  ii) When, in the opinion of GRANTEE, it is not advisable to
                  require the connection or to allow it at the time and in the
                  manner required by GRANTEE, taking into account the technical
                  development of the NETWORK or any other aspect that is deemed
                  relevant, provided that the MINISTRY has not expressed a
                  contrary opinion;

         GRANTEE must connect and provide services to any user that request such
         service, provided the user has terminal equipment approved by the
         MINISTRY. GRANTEE shall refrain from obligating the users to acquire
         equipment or other assets as a condition to provide the services
         subject matter of this concession.

5.2.     INTERCONNECTION WITH OTHER PRIVATE AND PUBLIC NETWORKS

         GRANTEE agrees to interconnect the NETWORK with other public networks
         authorized by the MINISTRY that request it in writing, as well as with
         private networks under the terms to be agreed upon.

         In the event an agreement for the interconnection services is not
         reached, the MINISTRY shall resolve such matter at its sole discretion.
         Furthermore, when the public interest demands it, GRANTEE agrees to
         combine its services with other authorized telecommunication services.

5.3.     COMMUNICATION OF USERS IN NETWORKS OF OTHER REGIONS

         GRANTEE agrees to carry out negotiations so that the users, if
         requested, may use the cellular radiotelephony services in the networks
         concessioned in other regions, as well as to permit users of other
         networks to use the NETWORK of the GRANTEE.

         If the parties fail to reach an agreement, the MINISTRY shall resolve
         the matter at its sole discretion.

         GRANTEE agrees take whatever measures deemed necessary to ensure that
         the users are able to intercommunicate with the radiotelephony networks
         of other operators.

5.4.     CAPACITY AND QUALITY FOR INTERCONNECTION

         GRANTEE agrees to install sufficient capacity to meet the demand of
         interconnection services in accordance with the technical standards
         approved by the MINISTRY and in accordance with the terms and
         conditions of the service agreements to be executed.



                                                                              16
<PAGE>   17
         GRANTEE covenants not to affect the quality or interfere in the
         rendition of the service of other interconnected networks or equipment.

5.5.     INTERCONNECTION WITH FOREIGN NETWORKS

         In the event that in order to interconnect the network of the GRANTEE
         with foreign networks it is necessary to execute an agreement with a
         foreign government, GRANTEE shall carry out all arrangements that may
         be necessary for the execution of the respective agreement, through the
         MINISTRY, acting as representative of the Federal Government.

         In the event the arrangements have to be made with a foreign company,
         the GRANTEE shall request the prior authorization of the MINISTRY for
         the execution of the interconnection agreement and shall submit true
         and complete copies of said agreements with the MINISTRY. The MINISTRY
         shall have the right to require amendments to said agreements whenever
         it deems that the interest of other network operators, the users of the
         network or those of the Mexican nation are unduly affected.

         Unless GRANTEE has grounds to do so, it shall not hinder any other
         authorized operator of telecommunications services from connecting its
         network to a network outside the Mexican Republic or from participating
         in any international agreement.







                                                                              17
<PAGE>   18
                                   CHAPTER 6

                  REGULATION OF RATES AND FINANCIAL EQUILIBRIUM

6.1.     APPLICABLE RATES

         GRANTEE shall submit to the MINISTRY for its approval the maximum rates
         for the services rendered in accordance with this concession. This
         rates shall be competitive at an international level. GRANTEE shall
         submit to the MINISTRY the studies of rates it has conducted, including
         progress in productivity and service costs.

         If, in the opinion of the MINISTRY, sufficient competition may arise in
         any of the services rendered by GRANTEE, a wider flexibility in rate
         control may be authorized.

         Competitive rates shall be formulated provided said rates are not based
         direct loss derived from the commercial exploitation of the public
         service subject matter of this concession.

6.2.     ACCOUNTING OF COSTS

         GRANTEE must maintain a service cost and income accounting system,
         where the performance of this items is identified.

         The accounting records mentioned in this paragraph must accurately
         reflect the costs (including capital expenditures), income, fixed
         assets used in the rendition of the services and liabilities
         attributable to said service. The MINISTRY may request from GRANTEE
         said reports for each fiscal year or for an specific term; but in no
         event shall this reports be requested more than every quarter.

6.3.     RATES IN PUBLIC BOOTHS

         The maximum rate for public boots shall be those authorized for urban
         and rural radiotelephone service.

6.4.     PUBLICATION OF RATES

         At least one a year, GRANTEE shall publish in the Official Gazette of
         the Federation and in the newspapers of widest circulation in Mexico,
         the maximum rates and charges for the services rendered in accordance
         with this concession.

6.5.     PARTICIPATION IN THE INCOME DERIVED FROM THE COMMERCIAL EXPLOITATION OF
         THE SERVICES

         In accordance with the provisions of Article 110 of the Communications
         Law, GRANTEE must pay to the Federal Government, as an initial
         participation, the amount of $19,789,

         000,000.00 (NINETEEN THOUSAND SEVEN HUNDRED AND EIGHTY NINE MILLION
         PESOS 00/100), as follows: 50% prior to the granting of this


                                                                              18
<PAGE>   19
         concession, 25% within a term not exceeding 90 calendar days from the
         date the concession is granted, and the remaining 25% within a term
         shorter than or equal to 180 calendar days. This term shall be computed
         from the date of this concession. In addition, GRANTEE shall pay to the
         MINISTRY an annual participation equal to 7% of the gross income
         derived from the commercial exploitation of the concessioned services.

         The above-mentioned participation must be paid by the GRANTEE to the
         Federal Government every six months within the first month following
         the expiration of the operating semester of service, in Mexican
         currency and in the offices of the Treasury of the Federation through a
         documents issued in favor of the latter.

         In the event that subsequently to the granting of this concession any
         other assessment or encumbrance is established in connection with the
         commercial exploitation and use of the general means of communication
         subject matter of this concession, or in the rendition of the mobile
         public radiotelephony service with cellular technology, the percentage
         of participation on income referred in this paragraph, shall be reduced
         in the same proportion.

         To guarantee payment of the outstanding percentages that correspond to
         the initial participation, GRANTEE obligates itself to deliver, prior
         to the granting of this concession, a bond in the amount of the
         respective payments, issued by an authorized bonding institution. The
         bond must include a statement to the effect that the bonding
         institution agrees to be bound by the provisions of articles 95 and 118
         of the Federal Law on Bonding Institutions and waives its rights of
         "order and execution". Such bond shall be issued in accordance with the
         format previously approved by the Treasury of the Federation.

6.6.     INVOICING

         GRANTEE shall invoice to the subscribers for an amount equivalent to
         the contracted services used. Said invoice shall be itemized and shall
         reflect the time used in long distance services or in interconnection
         with other regions, as well as the place to which each call was made.
         In addition, in the event special services had been contracted and
         rendered, such invoice shall provide a detailed description of such
         services.







                                                                              19
<PAGE>   20
                                   CHAPTER 7

                     INSPECTION, SUPERVISION AND INFORMATION

7.1.     INSPECTION

         The MINISTRY shall have at all times the right to supervise and inspect
         the installation and services rendered by GRANTEE, and GRANTEE shall be
         obliged to assist the MINISTRY in the performance of such inspections
         in accordance with all legal and regulatory provisions.

7.2.     ASSESSMENT OF EXPANSION GOALS

         Every six months, GRANTEE shall file with the MINISTRY a report on the
         progress of the expansion programs referred to under Chapter 3 hereof.
         On a yearly basis, the MINISTRY shall evaluate GRANTEE's compliance
         with the established goals.

7.3.     ASSESSMENT OF SERVICE QUALITY

         The MINISTRY shall review and asses the quality of the services
         rendered by the GRANTEE in accordance with the provisions of Chapter 4
         hereof. For the purpose of such assessment, the MINISTRY shall conduct
         aleatory, independent and permanent sampling of the qualities measured,
         thus verifying the information of GRANTEE's control systems.

7.4.     TECHNICAL AND STATISTICAL DATA

         GRANTEE agrees to file with the MINISTRY all technical, administrative
         and financial information in accordance with relevant legal and
         regulatory provisions. Such information shall be treated as
         confidential.






                                                                              20
<PAGE>   21
                                   CHAPTER 8

                        TERM, TERMINATION AND EXPIRATION

8.1.     TERM AND REVIEW OF THE CONCESSION

         This concession shall be in force for a term of 20 years which shall
         commence on the date of its publication in the Official Gazette of the
         Federation and, upon the parties agreement, shall be reviewed whenever
         required.

         Items of this concession such as expansion, update, operation, quality
         of services and rates shall be reviewed from time to time in accordance
         with the terms of this concession.

         In the event amendments are agreed, they shall become effective one
         year after they have been approved, GRANTEE, at its own cost shall
         publish in the Official Gazette of the Federation the amendments to the
         terms of this concession.

8.2.     EXTENDED TERM

         It GRANTEE has complied in all material respects with this concession;
         has not incurred in any of the events of early termination; has filed a
         written application to the MINISTRY with at least five years prior to
         the expiration of this concession, and accepts the new conditions which
         may be imposed in the rendition of the concessioned services; then, the
         MINISTRY may extend the term of this concession.

         No later than 180 days following the date on which GRANTEE filed its
         application in accordance with the preceding provisions, the MINISTRY
         shall decide on whether or not extend the term of this concession.

8.3.     RIGHT OF REVERSION

         Upon the expiration of this concession and of its extensions, if any,
         title over the assets used in the commercial exploitation of the
         concessioned services shall pass to the Mexican Nation in accordance
         with the applicable laws.

8.4.     EARLY TERMINATION

         In addition to the events set forth in the applicable laws and
         regulations, this concession shall terminate upon the occurrence of any
         of the following events:

                  a) If, notwithstanding a written admonition by the MINISTRY,
                  the services are not performed regularly and efficiently by
                  the GRANTEE in accordance with the established quality
                  standards.

                  b) If, without the prior approval from the MINISTRY, GRANTEE
                  suspends, totally or partially the services without justified
                  reasons.

                  c) GRANTEE fails to meet the expansion goals and conditions.



                                                                              21
<PAGE>   22
                  d) GRANTEE modifies or alters the authorized installations or
                  operating conditions of the concessioned service, without the
                  MINISTRY's prior approval.

                  e) If, after the written admonition from the MINISTRY, the
                  material terms and conditions established in this concession
                  are breached.

                  f) GRANTEE's refusal to interconnect with other
                  radiotelephonic service operators without justified reasons.

                  g) In the event GRANTEE permits that foreign investors have
                  control of more than 49% of the shares representing its
                  capital stock or have the power to determine management of the
                  corporation.

                  h) GRANTEE renders telecommunication services not contained in
                  this concession, without the MINISTRY's prior approval.

                  i) GRANTEE conceals or refuses to provide information to the
                  MINISTRY, without justified reasons.

                  j) voluntary or involuntary bankruptcy of the GRANTEE

                  k) GRANTEE's failure to pay to the Federal Government the
                  State's share of revenue.

                  l) If, in violation of the provisions of clause 2.10 hereof in
                  connection with cross subsidies and preferential treatment,
                  GRANTEE fails to comply with the MINISTRY's instructions.

                  m) GRANTEE disposes, assigns or transfers the assets required
                  for the public service, without the prior approval from the
                  MINISTRY.

         Early termination of this concession shall be subject to the procedure
         established in the applicable laws.

8.5.     REDUCTION OF THE SCOPE OF THE CONCESSION

         The scope of this concession for an specific area or service may be
         reduced in the event any of the conditions mentioned in paragraphs a),
         b) or c) of clause 8.4 arises in relation to such zone or specific
         service.

8.6.     GUARANTEE OR BOND

         In order to guarantee compliance with the obligations impose in this
         concession, no later than 30 days following the date of this
         concession, GRANTEE shall contract a bond in the amount of
         $1,500,000,000.99 (ONE THOUSAND FIVE HUNDRED MILLION PESOS 00/100) from
         an authorized bonding institution and in favor of the Treasury of the
         Federation. Said guarantee shall remain in full force and effect
         throughout the term of the concession. If in the opinion of the
         MINISTRY it becomes necessary to increase the amount of the bond.



                                                                              22
<PAGE>   23
         GRANTEE agrees to increase said bond within the 10 working days
         following the date on which the MINISTRY resolves about the increase.

         The bond must include a statement to the effect that the bonding
         institution agrees to be bound by the provisions of Articles 95 and 118
         of the Federal Law on Bonding Institutions and waives the benefits of
         "order and executio". The bond must be issued in accordance with the
         approved format of the Treasury of the Federation.

8.7.     SANCTIONS

         The MINISTRY shall apply the administrative sanctions set forth in the
         applicable laws and regulations regarding the services subject matter
         of this concession and those set forth in this concession, without
         affecting the right of any other authority to impose any other
         penalties or sanctions.

         Sanctions shall be imposed by the MINISTRY in accordance with the
         procedure set forth in Article 34 of the Communications Law.

8.8.     ADMINISTRATIVE AND JUDICIAL JURISDICTION

         For all matters related to this concession, except for those of an
         administrative nature which shall be resolved by the MINISTRY, GRANTEE
         submits itself to the jurisdiction of the Federal Courts of Mexico
         City, Federal District and waives any other jurisdiction it may be
         entitled to by virtue of its present or future domicile.

                                                      MEXICO CITY, JULY 23, 1990


   MINISTER OF COMMUNICATIONS                  SISTEMAS TELEFONICOS PORTATILES

       AND TRANSPORTATION                          CELULARES, S.A. DE C.V.


            (SIGNED)                                       (SIGNED)


      ANDRES CASO LOMBARDO                        GABRIEL ALARCON VELAZQUEZ



                                                                              23
<PAGE>   24
            AMENDMENTS TO THE TITLE OF CONCESSION GRANTED TO SISTEMAS
             TELEFONICOS PORTATILES CELULARES, S.A. DE C.V. FOR THE
                 RENDITION OF THE CELLULAR MOBILE RADIOTELEPHONY
                          SERVICES IN REGION 6 "CENTER"


                                   ANTECEDENTS

I. On July 19, 1990 SISTEMAS TELEFONICOS PORTATILES CELULARES, S.A. DE C.V.,
received a concession to build, install, maintain, operate and commercially
exploit for a term of 20 years a mobile public radiotelephony network with
cellular technology in the assigned frequency of 825-835/870-880 MHz for Region
6 "Center", encompassing the States of Aguascalientes, San Luis Potosi,
Zacatecas, Guanajuato, Queretaro and the municipalities of Huejucar, Santa Maria
de los Angeles, Colotlan, Teocaltiche, Huejuquilla, Mesquitic, Villa Guerrero,
Bolanos, Lagos de Moreno, Villa Hidalgo, Ojuelos y Encarnacion de Diaz of the
State of Jalisco.

II. The Ministry granted the concessions in the frequencies of cellular group
"A" through a public bid published in the Official Gazette of the Federation on
November 6, 1989. Said public bid set forth that the public service was to be
concessioned initially to only one entity and that interconnection rates similar
to those charged internationally would be applicable.

III. Pursuant to the general application prepared by the Asociacion Mexicana de
Concesionarios de Radiotelefonia Celular ("AMORCE"), based on the provisions of
clauses 2.4 and 8.1 of the Title of Concession for Region 6 "Center", on October
29, 1990, SISTEMAS TELEFONICOS PORTATILES CELULARES, S.A. DE C.V., requested to
the Ministry of Communications and Transportation the amendment of clause 6.5 of
the Title of Concession. Said application set forth that due to certain changes
experienced by the cellular telephony industry that affect the financial
equilibrium of the company, a review of the participation of the Federal
Government in the income derived from the rendition of the concessioned service
was necessary.





                                                                              24
<PAGE>   25
                                   WITNESSETH

I. WHERE AS, with the purpose of promoting the expansion, update and quality of
cellular mobile radiotelephony service, the Ministry deem convenient to process
the application of RADIOMOVIL DIPSA, S.A. DE C.V., for the exploitation of a
cellular mobile radiotelephony service in the area concessioned to your company.

II. WHERE AS, in order to cover the costs incurred in the rendition of the
service, and contribute to the expansion of the base local network, the Ministry
deemed convenient to authorize an increase in the rates charged for the
interconnection to the public telephony network above the international levels,
while in order to eliminate cross subsidies, for the period 1991-1996, Telmex's
rates for local services were authorized to increase gradually, as set forth
under Chapter VI of Telmex's Title of Concession.

III. WHERE AS, clause 2.4 of the Title of Concession of SISTEMAS TELEFONICOS
PORTATILES DE COMUNICACION, S.A. DE C.V., sets forth that the Ministry reserves
the right to grant to third parties other concessions to commercially exploit
within the same geographical area or in a different area, services identical or
similar to those granted to the receiver of the concession, for which purpose
the Ministry shall take into account the efficiency of the public service, the
financial stability of the receiver of the concession and the conditions of fair
competition.

IV. WHERE AS, the Ministry has conducted the technical and financial studies,
which show that the expected financial equilibrium for the concessioned service
was affected as result of the anticipated competition of the subsidiary of
Telmex and a temporally increased rate in the interconnection to the basic
telephony network above international levels (to enable Telmex to balance its
rate structure).

V. WHERE AS, the financial studies conducted by the Ministry further show that
the Federal Government's income was not affected due to the fact that Telmex's
subsidiary will pay in advance an equivalent amount for eight regional
concession in cellular frequency group "B".

VI. WHEREAS, in accordance with the foregoing antecedents and witnesseth and
based on the provisions of articles 36 of the Ley Organica de la Administracion
Publica Federal (Organic Law of the Federal Public Administration); 3, 4, 15, 51
and 85 of the Ley General de Vias de Comunicacion (General Law on
Communications); article 4, paragraph II and IX of the Reglamento de
Telecomunicaciones (Telecommunications Regulation) and clauses 2.4 and 8.1 of
the Title of Concession granted to SISTEMAS TELEFONICOS PORTATILES CELULARES,
S.A. DE C.V., and based further on the powers conferred to me by articles 4 and
5 of the Interior Rulings of this Ministry, it is hereby authorized to amend the
Title of Concession as follows:


                                    AMENDMENT

In accordance with the provisions of Article 110 of the Communications Law,
GRANTEE must pay to the Federal Government, as an initial participation, the
amount of $14,841'750,000.00 (FOURTEEN THOUSAND EIGHT HUNDRED AND FORTY ONE
MILLION SEVEN HUNDRED



                                                                              25
<PAGE>   26
AND FIFTY THOUSAND PESOS 00/100), as follows: $9,894'500,000.00 (NINE THOUSAND
EIGHT HUNDRED AND NINETY FOUR MILLION FIVE HUNDRED THOUSAND PESOS 00/100) prior
to the granting of this concession, the remaining amount in two equal
installments payable on November 30, 1991 and February 29, 1992. In addition, an
annual participation of 7% of the gross income derived from the commercial
exploitation of the concessioned services shall be paid to the Ministry.

VII. Each and every one of the conditions set forth in the Title of Concession
granted to SISTEMAS TELEFONICOS PORTATILES CELULARES, S.A. DE C.V., shall
survive this amendment.



                                                      MEXICO CITY, APRIL 1, 1991


                  MINISTRY OF COMMUNICATIONS AND TRANSPORTATION

                                  THE MINISTRY



                                    (SIGNED)

                              ANDRES CASO LOMBARDO



             SISTEMAS TELEFONICOS PORTATILES CELULARES, S.A. DE C.V.



                                    (SIGNED)



                          ANTONIO FERNANDEZ PALAZUELOS




                                                                              26