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 (204, 206, 208), the method comprising: the radio access network receiving a service request from a mobile terminal; the radio access network making a first core network selection; the radio access network sending the service request received to a core network selected as a result of the first core network selection requesting that the core network use a re-routing procedure to another core network (206, 208), the service request lacking identity information thus enabling the core network to determine that the radio access network needs to carry out circuit switched and packet switched coordination and for the core network to communicate with the mobile terminal in handling the service request and obtain from it the identity information; the radio access network receiving from the core network selected as a result of the first core network selection a re-routing message containing the identity information and a reject cause to indicate that the re-routing message is being used to provide the identity information to the radio access network for the purposes of circuit switched and packet switched coordination; the radio access network making a second core network selection; the radio access network sending the service request to the core network selected as a result of the second core network selection; and the radio access network storing any messages comprising reject causes received in response to sent service requests, until all available core networks have been tried or until an accept message is received in response to a sent service request. the radio access network receiving a service request from a mobile terminal; the radio access network making a first core network selection; the radio access network sending the service request received to a core network selected as a result of the first core network selection requesting that the core network use a re-routing procedure to another core network (206, 208), the service request lacking identity information thus enabling the core network to determine that the radio access network needs to carry out circuit switched and packet switched coordination and for the core network to communicate with the mobile terminal in handling the service request and obtain from it the identity information; the radio access network receiving from the core network selected as a result of the first core network selection a re-routing message containing the identity information and a reject cause to indicate that the re-routing message is being used to provide the identity information to the radio access network for the purposes of circuit switched and packet switched coordination; the radio access network making a second core network selection; the radio access network sending the service request to the core network selected as a result of the second core network selection; and the radio access network storing any messages comprising reject causes received in response to sent service requests, until all available core networks have been tried or until an accept message is received in response to a sent service request.