Misinformation alert! From Apple Discussions forums - found out they were wrong between ATT and TMO for IUP! So went into the Apple store to pick up a reserved 7+ with ATT as the carrier (could not find a TMO 7+ to reserve). The apple sales rep said I had to activate thru ATT and not thru T Mobile even though they are the same GSM phones. I could not upgrade and had to pay the full amount upfront.