A communication device for handling a user equipment, UE, Access Stratum, AS, context, the communication device comprising: a storage device, for storing instructions; and a processing circuit, coupled to the storage device, wherein the storage device stores, and the processing circuit is configured to execute, the instructions of: establishing a radio resource control, RRC, connection and a data radio bearer, DRB, with a first radio access network, RAN, of a first radio access technology, RAT; receiving a first RRC message via the RRC connection from the first RAN, wherein the first RRC message comprises a resume identity and indicates a RRC suspension; suspending the RRC connection from the first RAN in response to the first RRC message; the communication device being further characterised by: keeping the UE AS context, when the RRC connection from the first RAN is suspended; selecting a cell of a second RAN of a second RAT, the second RAT being different from the first RAT; determining that the UE AS context and the resume identity are invalid, discarded, in response to the selection of the cell of the second RAN of the second RAT; and transmitting, in response to the determination to discard the UE AS context and the resume identity and the communication device selecting a cell of the first RAN, a RRC connection request message to the first RAN. a storage device, for storing instructions; and a processing circuit, coupled to the storage device, wherein the storage device stores, and the processing circuit is configured to execute, the instructions of: establishing a radio resource control, RRC, connection and a data radio bearer, DRB, with a first radio access network, RAN, of a first radio access technology, RAT; receiving a first RRC message via the RRC connection from the first RAN, wherein the first RRC message comprises a resume identity and indicates a RRC suspension; suspending the RRC connection from the first RAN in response to the first RRC message; establishing a radio resource control, RRC, connection and a data radio bearer, DRB, with a first radio access network, RAN, of a first radio access technology, RAT; receiving a first RRC message via the RRC connection from the first RAN, wherein the first RRC message comprises a resume identity and indicates a RRC suspension; suspending the RRC connection from the first RAN in response to the first RRC message; the communication device being further characterised by: keeping the UE AS context, when the RRC connection from the first RAN is suspended; selecting a cell of a second RAN of a second RAT, the second RAT being different from the first RAT; determining that the UE AS context and the resume identity are invalid, discarded, in response to the selection of the cell of the second RAN of the second RAT; and transmitting, in response to the determination to discard the UE AS context and the resume identity and the communication device selecting a cell of the first RAN, a RRC connection request message to the first RAN. keeping the UE AS context, when the RRC connection from the first RAN is suspended; selecting a cell of a second RAN of a second RAT, the second RAT being different from the first RAT; determining that the UE AS context and the resume identity are invalid, discarded, in response to the selection of the cell of the second RAN of the second RAT; and transmitting, in response to the determination to discard the UE AS context and the resume identity and the communication device selecting a cell of the first RAN, a RRC connection request message to the first RAN.