A method of handling a service request in a communication system comprising a radio access network providing radio access capability to a plurality of core networks, the method comprising: a BSC in the radio access network receiving a service request from a mobile terminal; the BSC making a first core network selection; the BSC sending the service request received to a first MSC; the MSC communicating with the mobile terminal in handling the service request; the MSC sending an IMSI of the mobile terminal to the BSC; in the event that the core network selected as a result of the first core network selection does not provide service, the radio access network making a second core network selection; and the BSC sending the service request and the IMSI to the core network selected as a result of the second core network selection.