IPhone :: Retain Old Contract With New Number

Alright, first of all I know everyone is getting sick and tired of the iphone related threads popping up over here. But I have no other choice but to start one — hoping someone will be able to offer me a solution to my problem.

Here's the deal. My wife has the unlimited data plan, since she signed up with Att last year. Currently she has a iPhone 3GS and sees no need to upgrade to the new version.

I on the other hand had been using a paygo T-mobile plan (had been waiting for the iPhone).

Now the thing is she doesn't really use her data and I most definitely could with my shiny new phone (hopefully arriving on June 24th), but am unable to as I don't already have a contract with them.

I know people would suggest to switch the sims when I get the phone, but that's a no-go as the Misses is very attached to her number and does not want to change it (under no condition whatsoever)

So what I need all you guys to tell me is a way to get her number switched over to my contract so I can give her my sim (I'm aware of the sim differences in the two phones and will sort that out.

So any clue how to do this?

I was thinking of porting over her number to a different carrier and then porting it back to a new line on att (though this would mean I lose my preorder).

Though I don't know if I can port over her current ATT number and still maintain the contract. Does ATT allow that. And how difficult do you guys think it would be to port it back to a new connection on ATT.

Also, her number is originally from Wisconsin and now we live in Chicago.

Is there an easier solution?

Why can't ATT just switch the numbers on the contracts?