An example method includes a mobile terminal attempting to connect to a first radio access network, RAN, operating according to a first radio access technology, RAT. An indicia corresponding to the identifier of the recording medium is received from a client device upon the recording medium being input into the client device by a user. Thereby, the mutual trust between unknown users is improved, and the success ratio of adding an unknown user as a contact and the ratio of turning into a contact from an unknown user are increased.