https://www.att.com/support/article/wireless/KM1147710/
Reverse Number Lookup allows you to enter a U.S. number to get caller details. ... can alert you if you don't have a passcode or someone gains ...

https://www.reddit.com/r/ATT/comments/16sxpai/reverse_phone_lookup/
I have had AT&T the same number for 15 years. Is there anyway to get it scrubbed off the net from places like Spokeo and any reverse cell ...

https://www.nationalcellulardirectory.com/howto/att-reverse-phone-lookup/
... reverse phone lookup on ANY AT&T cell number ... Either way, you can't lookup cell phone, landline, or unlisted numbers on their website.