Abstract: A wireless telecommunication network communicates with a population of subscriber units. A portion of the subscriber units may be programmed to practice a less desirable service configuration, such as a default 13 kb/s vocoding process, even though capable of practicing a more desirable service configuration, such as enhanced variable rate coding (EVRC). Another portion of the subscriber units may not be capable of performing the more desirable service configuration. The network includes a database used to filter the application of a negotiation process during call setup for calls originating at the subscriber units. The negotiation process requests subscriber units to implement the more desirable service configuration. The database is automatically populated through an exchange of messages which occurs during a call setup process for incoming calls to the subscriber units.