Need help connecting to AT&T network after unlocking VZW g6

[Vyrrus2k9]

I unlocked my VZW g6 play by entering code in settings section to unlock phone (did not insert AT&T sim and wait for code request). It said code accepted but when I put in my AT&T sim I can't connect to their LTE network. It reads the sim, switches to global (gsm), and my network says AT&T with the proper phone number for that sim... But no 4g. I tried inputting the APN settings I found on several sites.. No luck. Same when I copied the APN settings from another AT&T prepaid phone I had available. No go. I called and asked for the APN settings from AT&T and they said I need to change the IMEI number on my sim to that of my g6. They said they did that for me. After power cycling the phone as instructed I still have no data service. Anybody have an idea what settings I need to use in order to use my AT&T sim? Or is that even my problem?