From my recent experience, it would seem by using Nokia's application,number can be blocked. By doing this, it also blocks SMS TEXT message even though this facility is not set in the Application set up. Blocking 'WITHHELD numbers also blocks TEXT message from that source. This latter situation has been bugging me for over a year and I have not been able to get a satisfactory solution from either of the Mobile Network operators I have been involved with. Both seem to point the finger at Nokia.