Just to clear things up....
(A) was it at some stage monitored, and at that stage had an active phone line, and now you dont wish for it to be monitored so have removed or disconnected the phone line or lead?
if so it will need to be re programmed to disable the dialer, you will need the installer code (not master code) to do this, or get a tech out to do it.
(B) has never been monitored and this has just come up?
If so how long since it was installed? are you sure the dialer isnt enabled?