no record of IMEI found? Cant Unlock my phone.

Hello!

I have a Samsung Galaxy S7, which my daughter gave to me for my deployment to Southwest Asia. This phone was completely paid off (I paid it off for her), however, when we attempted to unlock it via online (both via her AT&T account, and me as a non-AT&T customer), as well as telephonic, the AT&T reps continue to state that it is not an AT&T phone, that there's no record of it. BTW... this phone WAS used on the AT&T network for appx. 6 months. However, it boots up with the AT&T logo, and three (3) separate websites where you can search IMEIs, show it is in fact an AT&T phone.

So far AT&T has been completely useless, and when I return from my deployment, I am thinking about filing BBB and FCC complaints, as well as possibly pursuing legal action. This is the last attempt I make to AT&T to get this resolved, and it appears AT&T is violating federal regulations by not providing an unlock code for a paid-off AT&T phone.