How to Block Your Number on the iPhone
There may be times when you need to make a call but don't want your identity or phone number to show up on the caller ID of the person you're calling. There is an option on the iPhone to be able to easily turn off the caller ID and for your number to show up only as a "Blocked" number when making calls. Here are some easy steps to turn off the caller ID option.
Things You'll Need
How to block your number on the iPhone: Select the "settings" icon on your iPhone.
Scroll down to "Show My Caller ID" and select. If you are currently allowing your number to be seen, the button will be highlighted in blue and say "on". Hit the "on" button once. This will then switch it to "off".
When you make calls, your number will show up as "Blocked" to the person you're calling. Even if your friends have your number saved in their address books, the number will still come up as "blocked" and they will not be able to tell that it is your phone number.
To switch back to normal mode. Go through the process as above for "Show My Caller ID" and select "on" by tapping the "off" button once.