This clause illustrates the call setup of a non-Priority Service user attempting a Priority Service call. In this scenario, the user is not subscribed to Priority Service and call setup is not allowed to proceed.
A non-Service User dials the Priority Service prefix (e.g., *272) + Destination Number. The MS sends a Channel Request message to the BSS on the RACH channel. Having sent M + 1 Channel Request messages, the MS starts RR timer T3126. M is the value of the parameter "max retrans" broadcast on the BCCH.
The MSC/VLR detects the Priority Service prefix (e.g., *272) in the dialled digit string. The MSC/VLR determines from the caller's profile that the caller is not a Service User and rejects the request by stopping all running CC timers, responding with a Release Complete message to the MS with cause #63 "Service or option not available, unspecified", and releasing the MM connection.
On receipt of the Release Complete message, the MS stops all running CC timers and releases the MM connection. The MSC/VLR indicates that the radio resource(s) should be released by sending a Clear Command message to the BSS with cause "Response to MSC invocation".