It's far better to shove this up AT&Ts chute than simply walk off folks.
The risk will follow you to other carriers. This has to be stomped on or we're going to wind up back where we were in AMPS days, where there was no compatibility issue AT ALL but the carrier refusal to give you an unlock code meant that you had to toss your phone when you changed carriers EVERY TIME.
I lived through those days and that sort of tying arrangement was pervasive. Nobody's going to build wide-band handsets (that will work on all providers, or nearly all)
if there is no market for them due to this sort of restriction. If we lose that then we both lose choice AND wind up overpaying for our devices; it's already happening in the latter case as the DTEK60 compares favorably against devices that cost 40% more but are sold by the carriers. We're talking hundreds of bucks here folks...
Here's my latest on this -- the more exposure this gets on social media and similar, and thus the more noise that gets made, the better.
https://market-ticker.org/akcs-www?post=231609