I will order the iPhone X on the 27th. My current iPhone 7 is over eligible for an annual upgrade. I will basically be 14 payments into it on the 27th for a balance of $370. It is conceivable based on demand that I will be 15 payments into it when it arrives for a balance of $330. I am going to select the upgrade existing when ordering, but I am not sure I am actually going to trade it in. I am going to sell it on my own. My question: If I select upgrade (vs. a new plan), am I locked/bound to returning it? I believe the new X will just be another interest free loan and I can just pay off the 7?