how to get AT&T to stop sharing confidential other customer information with me?

Mark it as spam. 

This is how an AT&T employee replies to the company literally leaking peoples personal information to my private email?!? ROFL!!!

I have been marking it as spam for months and months and months now... and I continue to get details with peoples names, their birthdays, the amount of money they owe AR&T, and other details about their accounts... How is this remotely acceptable???

No the owner of the account inadvertently added your email so your getting their bills  in email. AT&T can’t and won’t help you locate the account holder. Only the account holder can correct it once they realize they aren’t getting emails. By the way with 700k employees you think every employee does email support? 

we are talking about PII leaks here. holy (Edited per community guidelines) what a dumpster fire data management at AT&T is lol

What do the emails say? If they are asking for information or confirmation then that is another sophisticated scam. If not, contact AT&T Billing, give them the information, and see if they can look into the account. It could also be as simple as an email error that needs to be corrected.

If you've been marking it as spam for "months and months" did you ever contact AT&T during that time?

The emails contain PII of other customers.  I am not going to waste my time in a phone queue to correct this.

Well, this is a public customer to customer forum only. It is not AT&T Support. There is nothing that anyone here can do. Either call Support or continue to mark them as spam.