Us all are users, just like you are. This is a user to user only forum. But even if you were speaking with anyone from Apple, they'd tell you no, they cannot unlock the phone to be used with another carrier. Only the carrier the phone is locked to can unlock it. NO ONE else can.
See this link --> How to unlock your iPhone for use with a different carrier - Apple Support
In a box just below the start of the article is the following statement:
"Apple can't unlock your iPhone for use with a different carrier. Only your current carrier can unlock your iPhone."
That means if the phone is locked to AT&T, ONLY AT&T can unlock it and you'll need to contact them and find if the phone is eligible (not all phones are) to be unlocked and what, if any costs you may be required to pay to unlock the phone. That will be between you and AT&T. If this sounds like a lot of work, maybe return the phone to Amazon and buy one which isn't unlocked. And by the way, ONLY Apple sells fully unlocked phones.