How To Block Your Cell Phone Number - Caller IDby Roger Chartier:
There are lots of reasons that you would want to block your cell phone number.
If they know it's you, they might not answer the phone while they are up to no good or in flagrante delicto.
When your call gets through, don't speak just listen very carefully for background sounds that would give you a clue as to where they really are.
One trick is to use another person or change your voice to ask to put whomever they say (probably a lie) they are with on the phone.
Ok, You can permanently block your phone number or you can do it for individual calls as you choose:
I am not sure if it legal, but with a blocked number, unless they recognize your voice you can give them holy hell and bust their nuggets without recourse.
To do it once, dial * 67 like this *67 (777) 777-7777.
This doesn't block calls from any emergency services or toll free numbers.