So here's a semi-hypothetical. Think I know the answer but figured asking might get me some additional info. 1. Have an iPhone on AT&T Next. About 2/4 through the payments to the point where I could trade it in for an upgrade. 2. Interested in buying another iPhone outright (full price) and using it on my account/line. 3. This would mean swapping out the iPhone that is currently being paid for via Next, with a different phone that I fully own. 4. Note that I'm not trying to get out of the Next payments, I'd be completely fine continuing to pay for the Next phone through the end of the Next payments; I'd just want to be using a different iPhone on my account/line. In my head this wouldn't be a problem because AT&T would just keep charging me for the Next payments regardless of whether or not it was the active phone. But the reality seems to be that I could not actually do this. Anyone have any experience here? Thanks!