I have an iPhone 6 Plus 64GB AT&T that I got last Sept on 2 year contract pricing. Normally I would wait the 2 year cycle and then upgrade to the 7, skipping the S generation. Might still do that. I see that a new Plus S 64GB is $849 full price as I can't get next pricing until April 2016. Can I sell my iPhone 6 Plus and just pay the $850 for the unlocks 6 S Plus 64? As long as I pay my contract pricing for the next x months or whatever, does it matter what phone is on my plan? And can I sell my current 6 Plus to an AT&T customer (since I am guessing it cannot be unlocked until sometime next year)? Thanks for any info.