I recently sold my first generation iPhone on an auction site. I wanted to make sure that all of my personal information wasn't left on the phone so I went to my local Apple store to get instructed. They informed me that restoring my phone in iTunes without requesting a back up was all that was needed.

I had already done this and sure enough, all of my contact info, songs, videos and apps were purged from the phone. What was still on the phone however was my old phone number. I wasn't thrilled about somebody knowing my phone number as it is now the number of my 3G phone. Also, I was wondering what else I may have missed.

The Apple rep said they did not know how to do anymore then what I was told, so I trekked upstairs at my local mall to the AT&T store where I got the following instructions:

Go to "Settings"
Choose "General"
Choose "Reset"
Choose "Erase All Content and Settings"

That's it! It takes a little over an hour for the settings to be wiped.

Use this carefully as it will reset your phone to the original state it came in out of the box.