GoPhone Email Address provided by CRS invalid. . .

Calling 611 from a phone I purchased at Best Buy the care agent told me in order to resolve the issue I first needed to send a proof of purchase to gophonesolutions@att.com. However, the email comes back invalid. I clarified all the information she gave me to make sure I was not missing a step or hearing anything wrong. I am not happy to start with seeing that I purchase this as a gift for my daughter and paid top dollar for a phone Apple doesn't even make anymore but I already wasted time on the phone with AT&T only to be provided incorrect information from an incompetent agent. I wish I could still return the phone back to Best Buy but since I purchased this gift early and Best Buy only offer 14 day return I am stuck. I need this resolved quickly