A modem for use at a terminal, the modem comprising: a first interface arranged to connect to a communications network; a second interface arranged to connect to a host processor on the terminal; and a processing unit, the processing unit configured to: detect that a call is to be established over the communications network; in response to said detection, perform a call setup procedure; determine if the call setup procedure has been successful or has failed due to failure of a security procedure; and in response to determining that the call setup procedure has failed due to failure of a security procedure, repeat said call setup procedure without indicating failure of the call setup procedure to a user of said terminal.