I don't know anything about the buy one get one deal, because my wife and I would have to agree on what makes for a good phone. Fat chance there.
I would imagine it's the same, though. Pay off all the monthly payments and keep both, wth the bill credit continuing afterwards, and then decide what to do thereafter. Or turn it in after 12 (I don't know what happens to the free one) and do another Next or buy one from ATT. If you do another Next, you get the bill credit. If you buy outright from ATT (and you'll have to buy from them) you won't get the bill credit. You only get the bill credit if you do a Next plan or bring your own device, but not if you pay full upfront, as I recall. Seems counterintuitive. But that's how they get you to keep upgrading through them.
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