How do you remove a phone number from a cell phone?

I have a BlackBerry 7290 and I want to sell it on Ebay but my phone number is set to the phone. I was wondering how you could make it blank and just a plain phone without the number.

The phone number is in the sim chip. You should be able to remove the sim chip, and perform some sort of master reset on the blackberry. Even so, when the next owner put's their sim chip in it, it would display their own number.

There should be options when you go to the numbers...There you can delete it!