Sim pin network MottoG Dont have a clue what carrier the phone is locked to

[AC Question]

Recently bought a motto g off of a friend. The phone was originally purchased off of Amazon and was unlocked to all carriers. Somewhere along the line the phone became locked assuming because it asks for sim pin network code when I put my att sim in it. No one knows what carrier it's locked to. Mottorola nor att c.s. have been able to help. Someone pleeeeeaaase help me I'm currently using a razor from 1992 lol