The procedure for blocking an incoming number depends on the telephone service provider but in general, the person wanting to block a number must activate the call blocking service, if available, and specify the number to block. Verizon customers can activate call blocking by dialing 1160.
After activating the call blocking service, the customer must set up the "blocked call" list. Callers whose numbers appear on the list reach a recording advising them that the party they are trying to reach is not accepting calls at this time. Call blocking normally cannot block certain calls, such as those from outside the local area or from cell phones.