A method and apparatus for providing both Mobile Terminated, MT, and Mobile Originated, MO, circuit switched (CS) services such as Short Message Service, SMS, services in networks utilizing CS Fallback and CSoLTE-I architectures. An extended SGs interface referred to as SGs+ (63) is implemented between a Mobility Management Entity, MME, (64) in an SAE core network (11) and a Mobile Switching Center Server, MSC-S, (61). The SGs+ interface supports transmission of upper layer CS packet data units while utilizing either connectionless or connection-oriented Signaling Connection Control Part, SCCP, operation. The non access stratum, NAS, signaling support between the User Equipment, UE, (27) and the MME (64) is extended to provide support for both MT SMS and MO SMS service.