I did the $650 trade in with AT&T and got a 7 plus. I know to get the full $650 credit I have to keep my 7 plus for 2 years. So my question is.... If I want a new phone next year, can I use my 7 plus next year as a trade in with the Apple Upgrade Program and continue to pay for the 7 Plus on my AT&T bill even though I turned it into Apple. Or I was thinking, I still have the old unlimited plan and I can add another line for $9.99 and could I do that and get a new iPhone but never use it on the new "dummy" line. I know I would be paying for 2 phones either way if I want to get the full $650 credit for the iPhone 6 I just turned in. Or will I have to pay full price next year and continue to pay for 24 months for the 7 Plus I just got