Equiptment Destroyed in a House Fire

On November 14, 2019 we had a major house fire that destroyed the entire contents, including the AT&T 2-Wire Uverse modem. When I notified AT&T of the fire, the customer service representative said since the modem was destroyed, I did not have to return the modem. We didn't notice at first, but only the monthly usage charge was dropped from the bill. I called again a few months latter asking why I was still being charged for the modem. They cancelled the account and I was left with a small negative balance. Now I have been sent a bill demanding payment for the destroyed modem. I called AT&T about the bill. The custome service agent, John 1043, response was pay up or we turn you over to collections.

So who do I contact at AT&T to try to get this resolved?