MMS messaging fail

Looking for help. Unlocked verizon S7 Edge on ATT network. SMS texting works but cannot send or receive MMS messages. 1.5 hours on the phone with ATT changing APN values and other assorted things to no avail.
ATT created a Case number so we'll see where that goes. The phone is brand new, I contacted the seller and they said to install a different messaging app than the default. I tried Textra and Go SMS Pro. Nothing. Any help is appreciated

from DroidForums.net | Android Forums & News http://ift.tt/2DGNflL
via IFTTT