If the network does not support the call rearrangement procedures, it shall reject a SUSPEND message according to the error handling procedures of 5.8.4. If the network supports the call rearrangement procedures on a subscription basis, but the user does not subscribe to the service, the network shall reject a SUSPEND message with cause No. 50, requested facility not subscribed; the Cause information element shall not contain a diagnostic field under these circumstances.
On receipt of a SUSPEND message, the network will respond by sending a SUSPEND REJECT message with cause No. 84, call identity in use if the information contained in the SUSPEND message is not sufficient to avoid ambiguities on subsequent call re-establishment. This will apply, in particular, when at a given user-network interface, a SUSPEND message is received with a call identity sequence already in use, or when the SUSPEND message does not contain any call identity sequence and the null-value call identity is already allocated for that interface. On receipt of the SUSPEND REJECT message, the user shall stop timer T319, and return to the active state. If timer T319 expires, the user shall notify the user application and return to the Active state.
In these cases the state of the call is not altered within the network (i.e. it remains in the Active state).