[li4alex]

I unlocked my phone, had the APN changed, but cannot get on the LTE plan and am stuck on the generic smartphone plan, with much slower speeds at the same cost, as expected. AT&T phone support had escalated my case to a back office, who said that because my phone is not from AT&T, their system cannot add my phone to the LTE plan. Just a heads-up for anyone else that might want to do this, although I'd be thrilled if anyone has tips that could get me on the LTE plan.

Edit:
I was able to get the LTE plan by returning to the AT&T store and asking for it. The tech added the LTE plan, but then entered the non-LTE APN. Once I added the LTE APN, I had LTE functionality.