Press the green talk button, press BB button, next to the green talk button, then select options, general options, you will see show number, click on that and select no
Posted from my CrackBerry at wapforums.crackberry.com
Both are excellent suggestions. I've used *67 individually and have also made the adjustments to my phone. I've gone so far as to add the *67 to numbers in my contact list and saved them. That way, these particular contacts can't see my number.