How can you block your phone number when making a call on your Cingular phone?

Dialing *67 before the number will prevent your number from showing up on caller ID or being retrieved via *69.

On a Cell Phone you need to dial #31# before you number *67 wont work on a cell phone(not in Canada anyways)

This is what works for me when I need to block cell numbers http://howtofixstuff.blogspot.com/2012/03/how-to-block-numbers-on-cell-phone.html