Got phone from grandpa, it's carrier locked to AT&T but I'm not AT&T, he passed away, I don't know what to do
My grandpa bought a new iPhone XR but passed away not long after, he gifted me the phone right before he died. This phone is literally the last thing I ever got from him. The thing is, I'm not an AT&T customer and the phone is locked to AT&T. No one has access to his account so I don't know if he paid off the phone or not and I can't pay it off if it isn't. I just can't trade it in or something like that either, gifting me this phone was literally one of the last things he did. I can't seem to get ahold of an actual person with AT&T customer service either. I don't know what to do. I don't know if there's anything I can do. I know it's a complicated issue, but any advice?