How to retrieve the user’s phone number programmatically in iphone application?
No correct solution
I don't believe it is possible with the 2.2.1 SDK.
Wil Shipley worked very hard on this and talked about it at his presentation to a bay area cocoa heads group back in april. Google wil shipley cocoa heads vimeo if you want to watch it.
I haven't tried myself.
I had the same issue and resolved it by setting the number on the phone. By default I do not think that the number is set on the iPhone but that can resolved by going into Settings->Phone->My Number.