A communication method for maintaining service continuity performed by a User Equipment, UE, in a wireless communication system, the method comprising: detecting a change in a tracking area in which the UE is located within a first Radio Access Technology, RAT, wherein the UE is registered in a core network of the first RAT and a core network of a second RAT; initiating a registration procedure or a tracking area update procedure in the first RAT with a new management entity, being either an Access and Mobility Management Function, AMF, or a Mobility Management Entity, MME, in the core network of the first RAT; receiving, from the management entity, a registration reject message or a tracking area update reject message; transmitting to the new management entity in the core network of the first RAT, a registration request message or an attach request message including a registration status information of the UE of the second RAT and the UE native Globally Unique Temporary Identifier, GUTI, of the second RAT and the UE GUTI associated with an old mobility entity of the first RAT as to configure the management entity to transmit, to at least one of a Home Subscriber Server, HSS, and User Data Management, UDM, information indicating that a registration of a management entity in a core network of the second RAT is required not to be deleted and, wherein the registration status information of the UE of the second RAT comprises at least one of Evolved Packet System, EPS, Mobility Management, EMM registration status information set as one of the UE is not in an EMM-REGISTERED state and the UE is in the EMM-REGISTERED state when registering at the AMF, or 5GMM registration status information set as one of the UE is not in a 5GMM-REGISTERED state and the UE is in the 5GMM-REGISTERED state when registering at the MME, wherein the first RAT is a 3rd Generation Partnership Project, 3GPP, New Radio, NR, RAT and the second RAT is a Long Term Evolution, LTE, RAT or the first RAT is a 3GPP LTE RAT and the second RAT is a 3GPP NR RAT. detecting a change in a tracking area in which the UE is located within a first Radio Access Technology, RAT, wherein the UE is registered in a core network of the first RAT and a core network of a second RAT; initiating a registration procedure or a tracking area update procedure in the first RAT with a new management entity, being either an Access and Mobility Management Function, AMF, or a Mobility Management Entity, MME, in the core network of the first RAT; receiving, from the management entity, a registration reject message or a tracking area update reject message; transmitting to the new management entity in the core network of the first RAT, a registration request message or an attach request message including a registration status information of the UE of the second RAT and the UE native Globally Unique Temporary Identifier, GUTI, of the second RAT and the UE GUTI associated with an old mobility entity of the first RAT as to configure the management entity to transmit, to at least one of a Home Subscriber Server, HSS, and User Data Management, UDM, information indicating that a registration of a management entity in a core network of the second RAT is required not to be deleted and, wherein the registration status information of the UE of the second RAT comprises at least one of Evolved Packet System, EPS, Mobility Management, EMM registration status information set as one of the UE is not in an EMM-REGISTERED state and the UE is in the EMM-REGISTERED state when registering at the AMF, or 5GMM registration status information set as one of the UE is not in a 5GMM-REGISTERED state and the UE is in the 5GMM-REGISTERED state when registering at the MME, wherein the first RAT is a 3rd Generation Partnership Project, 3GPP, New Radio, NR, RAT and the second RAT is a Long Term Evolution, LTE, RAT or the first RAT is a 3GPP LTE RAT and the second RAT is a 3GPP NR RAT.