A remote call center utilizes both cell phone and satellite communication networks to transmit data messages to a vehicle equipped with both a telematics module and a SDAR module. The telematics module and the SDAR module are both coupled to a vehicle data bus, and a software communication token containing a current budget is assigned to a selected module in response to a vehicle turn-off event. The module possessing the communication token determines the available signal strength on its respective communication network. If the available signal strength is adequate for reliable data communication with the call center, the module retains possession of the token and periodically wakes-up to check for incoming messages from the call center. If the available signal strength is inadequate, the module possessing the token passes the token to the other module, after which that module periodically wakes-up to check for incoming messages from the call center.