This isn't right, I've for sure done this with IUP and directly with Apple, without having to deal with T-Mobile at all.I offered to do exactly that and the dude told me I had to buy out the phone completely. It’s funny cause one of the reasons I went to apples upgrade program was cause I got tired of dealing with T-Mobile’s BS when I wanted to upgrade my phone and now they give me this crap.
Sounds like their IUP/T-Mobile integration is a bit messed up right now, so let's all wait a day or 2 for them to figure things out.