The operation of a conventional cellular telecommunications transceiver that forms part of a vehicle's telematics system can be selectively changed in order to provide telephone calls by providing the transceiver with a second and different SIM card. Providing a second SIM card, however, will disable telematics service that can include stolen vehicle tracking. A personal identification number or PIN is thus required in order for the information that is stored in an external, user-provided SIM card to be used by a telematics system transceiver rather than the information stored in a built-in SIM card that is provided by a telematics system operator/provider.