We can't unlock this device for you because AT&T did not sell or activate it.

I bought an iphone 12 second hand from a website called backmarket. They told me that the phone was completely unlocked and i would have no issues connecting it to my carrier. Upon the phones arivial i took it to my carrier(MetroPcs) and they told me that the phone was carrier locked and i would have to get it unlocked before connecting it to them. They directed me to a local buisness called the phone doctor that wouldunlcok the phone for me. They then told me that they are no longer allowed to unlock phones and that i would have to go to the place where the phone was carrier unlocked to(At&t). i went there and then they told me that they cant unlock phones in store, an employee then directed me to a website that could do it for a small fee. i payed $21 for a consolation fee then another $32 for them to "finish" the process, after a few back and forth messages with their support team i read the reviews and realized i had been scammed. Now im here wondering if theres anyway i can unlock this phone but i cant seem to find one. Can anyone help?