The present application relates to a user accessing to a visited network in a wireless telecommunication network. After receiving an access request from the user for selecting a visited network and detecting the visited network selected by the user has changed, an AAA server device initiates a request for obtaining authentication and/or authorization information of the user from a HSS. In the process of obtaining the authentication and/or authorization information, the HSS checks whether the user is authorized to access to the visited network according to a list of authorized visited networks stored in the HSS.