A method and an apparatus for operating a timer in a wireless transmit receive unit (WTRU) are described. In one scenario, the method includes the WTRU receiving a circuit switched (CS) call request and a CS service notification, transmitting an evolved packet system mobility management service request (ESR) message, starting the timer, and stopping the timer upon reception of a handover command or a cell change command to indicate a successful CS fallback procedure. In another scenario, the method includes the WTRU receiving a CS call request and a CS service notification, transmitting an ESR message including a CS call rejection indication, starting the timer, and stopping the timer upon reception of an acknowledgement that the ESR message was transmitted or received to indicate a successful CS fallback procedure.