Seller sold me a Blacklisted phone, what can I do?

I bought an iPhone XR at a store may Be about 6 months ago. I should’ve been on alert when the seller was saying the phone was unlocked, but not to reset the phone. Anyways I moved from att to Metro PCS and while trying to get the SIM card to work, they said that the phone was blacklisted. Which is weird because... show more I bought an iPhone XR at a store may Be about 6 months ago. I should’ve been on alert when the seller was saying the phone was unlocked, but not to reset the phone. Anyways I moved from att to Metro PCS and while trying to get the SIM card to work, they said that the phone was blacklisted. Which is weird because att took the phone and I was able to use their services. What can I do? Go back to the store? I know that Indian guy will try his best not to return it, especially after 6 months.
Update: Should I call the police as well? Onsite if he doesn’t want to do anything?
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