An apparatus, method and system are disclosed for providing a default mode for authentication failures in a mobile telecommunication network. The system includes an authentication center (typically co-located within a home location register), an adjunct network entity, and an originating mobile switching center. The home location register generally stores information pertaining to a mobile unit, such as a cellular or PCS mobile telephone. The adjunct network entity contains one or more application nodes, such as an announcement application node for providing an announcement on a call leg to the mobile unit. When the network has been accessed by a mobile unit through a call leg, the originating mobile switching center is configured to perform an authentication procedure. The originating mobile switching center further is configured, when the authentication procedure has resulted in an authentication failure, to receive a message from the authentication center to deny the mobile unit access to the network, to terminate a communication session with the mobile unit, and to route the call leg to the announcement application node for the provision of an announcement on the call leg to the mobile unit. Following such an announcement, the originating switching center is also configured to route the call leg to a customer service center, for example, to reprogram the mobile unit.