unlocking apn settings

[roadking 05]

hi all. Just bought a s5 unlocked (supposedly) new att version on ebay. My carrier is consumer cellular. I can make calls, texts but that's about it. The apn settings are in the att settings and cannot be changed. My carrier says they cant do anything more. Samsung says att was the original owner, and they wont do anything. The seller says he sold me an unlocked device. no one seems to be able to help, is this a common problem. Thanks in advance. Ernie

 

[roadking 05]

What I have learned since my post. The phone is SM-G900A An att hybrid. Non Samsung firmware. Guess its going back. Can I expect the same problems with other variants? I have done this with earlier un-locked gms phones.