A Mobility Management Entity MME comprising circuitry configured to: receive, from a user equipment and via an eNB of a packet-switched portion of a wireless telecommunications network, a request to establish a call using a circuit-switched portion of a wireless telecommunications network (210, 310, 410, 545), wherein the request is an extended service request including service type information that describes the call as a circuit-switched Unrestricted Digital Information UDI video call; and determine (220, 320), based on the request, a call type of the call; characterized in that the circuitry is further configured to: identify,, based on the call type, a type of radio access network, of a plurality of radio access networks capable of supporting different call types and including an UTRAN or a GERAN, that can support the type of the call requested by the user equipment, each of the plurality of radio access networks being connected to the circuit-switched portion of the wireless telecommunications network; communicate (240, 250, 330), to the packet-switched portion of a wireless telecommunications network, a request to establish the call using the identified radio access network; transmit a context modification message to the eNB, the context modification message including information informing the eNB that a Circuit-Switched Fall Back CSFB procedure for the call should be executed toward the UTRAN instead of the GERAN; and receive a modification response message from the eNB, wherein the modification response message confirms assistance and compliance of eNB with respect to the CSFB procedure being requested. receive, from a user equipment and via an eNB of a packet-switched portion of a wireless telecommunications network, a request to establish a call using a circuit-switched portion of a wireless telecommunications network (210, 310, 410, 545), wherein the request is an extended service request including service type information that describes the call as a circuit-switched Unrestricted Digital Information UDI video call; and determine (220, 320), based on the request, a call type of the call; characterized in that the circuitry is further configured to: identify,, based on the call type, a type of radio access network, of a plurality of radio access networks capable of supporting different call types and including an UTRAN or a GERAN, that can support the type of the call requested by the user equipment, each of the plurality of radio access networks being connected to the circuit-switched portion of the wireless telecommunications network; communicate (240, 250, 330), to the packet-switched portion of a wireless telecommunications network, a request to establish the call using the identified radio access network; transmit a context modification message to the eNB, the context modification message including information informing the eNB that a Circuit-Switched Fall Back CSFB procedure for the call should be executed toward the UTRAN instead of the GERAN; and receive a modification response message from the eNB, wherein the modification response message confirms assistance and compliance of eNB with respect to the CSFB procedure being requested. identify,, based on the call type, a type of radio access network, of a plurality of radio access networks capable of supporting different call types and including an UTRAN or a GERAN, that can support the type of the call requested by the user equipment, each of the plurality of radio access networks being connected to the circuit-switched portion of the wireless telecommunications network; communicate (240, 250, 330), to the packet-switched portion of a wireless telecommunications network, a request to establish the call using the identified radio access network; transmit a context modification message to the eNB, the context modification message including information informing the eNB that a Circuit-Switched Fall Back CSFB procedure for the call should be executed toward the UTRAN instead of the GERAN; and receive a modification response message from the eNB, wherein the modification response message confirms assistance and compliance of eNB with respect to the CSFB procedure being requested.