keep getting notified about someone elses bill, help

There is nothing you can do about the email address on an account that isn’t yours. As you already found, ATT won’t even talk to you. Only the account owner can change the email address associated with their account. Hopefully, they’ll eventually notice and update their account. You should just ignore, delete or mark the emails as spam.

appreciate your feedback. been "ignoring" it for almost a decade now. looking for a response from an ATT person. 

Thank you for bringing this to our attention, @pertuberbedbybillnotificationstowrongemail. We want to help you with that!

I am sending you a Direct Message (DM) which you can find by navigating to the top right corner of the Forums page. The icon is a chat bubble containing stacked lines. It is located next to the notifications. Please reply to the message in the DM.

Lar, AT&T Community Specialist

Sounds like you've already received responses from "an ATT person" each time you've called. You aren't looking for a response from AT&T, you're looking for a response that tells you what you want to hear.

@pertuberbedbybillnotificationstowrongemail 

People can put whatever phone number or email for contact info. Maybe it was a typo, maybe they did it on purpose to avoid notifications. But that is up to them, just like you putting a whole thread topic as your user name. It may not be very appropriate, but it is individual choice.

Though I see the official help team is sending you a DM. If they end up reaching out to the account owner to resolve this, it would be great. I just wouldn't get hopes up too high.