Methods and apparatus performed in a wireless communication system are provided. An attach request message for a first network supported by a user equipment (UE), is transmitted to a management entity. The attach request message includes first UE network capability information indicating support of a second network supported by the UE. An attach accept message indicating completion of attach to the first network is received from the management entity. A packet data network (PDN) connectivity request for the first network is transmitted to the management entity. A first session for the first network is established through a session management entity supporting mobility between the first network and the second network. In case that the UE supports the second network, regardless of enabled or disabled status of UE network capability for the second network, the session establishment request includes information related to a second session for the second network.