The iPhone 4s isn’t the big upgrade everyone was hoping for. It doesn’t seem like a bad upgrade, but there is probably little to the handset that makes users of the iPhone 4 want to upgrade. Those still on a 3G or 3GS will probably feel differently.
However, Apple is making it a bit easier to upgrade for those eligible to purchase the handset at $200. How is that? They are offering $200 for an iPhone 4 in like-new condition (via 9to5Mac). Users willing to jump in and go for another two-year contract can trade their iPhone 4 in with Apple and use that $200 to pay off their new handset. 16GB iPhone 4S for trading in your old device. Or, you can just pay extra and get yourself the 32GB or 64GB, $299 and $399 respectively.
Not a terrible deal if you qualify. Of course, that probably means that you paid quite a bit for your iPhone 4 as you likely didn’t qualify back then.

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Is the rebate tied into an extended contract with a service provider? I’ve got an iPhone 4 that I can’t make or receive phone calls on, so I’m anxious to switch carriers, even though I’ll have to pay a termination fee. If it means they won’t offer me anything for my old phone I’m going to be pissed off.
You will be able to sell your iPhone 4 and cover any termination fees. Call ATT and find out how much they will charge you