A User Equipment, UE, comprising: a wireless transceiver, configured to perform wireless transmission and reception to obtain one or both of a 3rd Generation Partnership Project, 3GPP, access and a non-3GPP access; and a controller, configured to communicate with one or both of a first 3GPP core network and a second 3GPP core network over one or both of the 3GPP access and the non-3GPP access via the wireless transceiver, wherein the first 3GPP core network and the second 3GPP core network are different and wherein the communication with one or both of the first 3GPP core network and the second 3GPP core network comprises: receiving, from the first 3GPP core network, a reject message without integrity protection; and searching for another suitable cell, when the reject message is received over the 3GPP access and the UE is registered with the first 3GPP core network over the non-3GPP access, or when the reject message is received over the 3GPP access and the UE is registered with the second 3GPP core network over the 3GPP access or the non-3GPP access; or searching for another suitable Access Point, AP, when the reject message is received over the non-3GPP access and the UE is registered with the first 3GPP core network over the 3GPP access, or when the reject message is received over the non-3GPP access and the UE is registered with the second 3GPP core network over the 3GPP access or the non-3GPP access. a wireless transceiver, configured to perform wireless transmission and reception to obtain one or both of a 3rd Generation Partnership Project, 3GPP, access and a non-3GPP access; and a controller, configured to communicate with one or both of a first 3GPP core network and a second 3GPP core network over one or both of the 3GPP access and the non-3GPP access via the wireless transceiver, wherein the first 3GPP core network and the second 3GPP core network are different and wherein the communication with one or both of the first 3GPP core network and the second 3GPP core network comprises: receiving, from the first 3GPP core network, a reject message without integrity protection; and searching for another suitable cell, when the reject message is received over the 3GPP access and the UE is registered with the first 3GPP core network over the non-3GPP access, or when the reject message is received over the 3GPP access and the UE is registered with the second 3GPP core network over the 3GPP access or the non-3GPP access; or searching for another suitable Access Point, AP, when the reject message is received over the non-3GPP access and the UE is registered with the first 3GPP core network over the 3GPP access, or when the reject message is received over the non-3GPP access and the UE is registered with the second 3GPP core network over the 3GPP access or the non-3GPP access. receiving, from the first 3GPP core network, a reject message without integrity protection; and searching for another suitable cell, when the reject message is received over the 3GPP access and the UE is registered with the first 3GPP core network over the non-3GPP access, or when the reject message is received over the 3GPP access and the UE is registered with the second 3GPP core network over the 3GPP access or the non-3GPP access; or searching for another suitable Access Point, AP, when the reject message is received over the non-3GPP access and the UE is registered with the first 3GPP core network over the 3GPP access, or when the reject message is received over the non-3GPP access and the UE is registered with the second 3GPP core network over the 3GPP access or the non-3GPP access.