Just got back from my local T-Mobile store. They were very unsure about how to handle things and admitted that nothing official had been decided yet and that there was no set procedure in place. I was the first customer to try and return the Note 7.
I told them things that I had read on T-Mobile's website (that I could return my phone even if i was outside the the 14 day window) and 2/3 of the employees said "no, that's wrong," but one of the employees got on the phone and called someone who said I could return it no matter what, and to ring it up as a "no receipt return." So they did this for me.
I wanted to make sure that this wouldn't affect my JOD status, and that I'd still get my 2 jumps this year. They said "yes, you will." But once they had processed my transaction (swapping Note7 for S7Edge) it actually took me OFF of JOD. Yikes. They don't offer JOD anymore, so I was really worried about being able to get it back. They tried a few different ways to add JOD back, but it didn't work. Finally they did something, but said I would have to pay $20 upfront to get back on JOD, but that they would credit my account the $20 to zero it out.
So, all in all, they were very helpful and nice, but it seems like there is still a lot of misinformation going around. So if you go to a T-Mobile and don't get the answers you want, talk to another salesperson in the store and/or have them call whomever it is they call when they need help.