Someone sold me a stolen iphone 4s? Beside contacting who sold me the phone what should I do?

I brought this phone from someone I know.(we're not friends, we had classes talked occasionally, and graduated from high school together last year). He put on instagram that he's selling an iPhone 4s for $150 and DM if for more info. We'll I DM and ask if they were anything wrong with or did it have any problems? And he said no. So we set up a time and place later that day. When he met he also had a friend with him, he said that it's his friend that is selling the phone. So I looked at the phone to make sure it isn't cloud locked and restored it to factory settings. Since I wasn't in an area that had Wi-Fi, I couldn't set up the phone. I spent the night at my cousins house and she doesn't have internet to her house so I still could set up the phone. When I woke up the next day, I drove to my house to get ready for work. I was able to set up the phone and everything, i just could connect to Wi-Fi. (before I brought this phone I had brought and iPhone 4 from gamestop for $238. Since I brought the iPhone 4s for $150, I wouldn't need the 4 anymore and also I figured I got a good deal on a newer phone.) anyway when I when on break at work I tried make a phone call be it wouldn't go through, since i was to work all day i couldn't call at&t to fix this problem because by the time i got off, they were closed. So this morning i call at&t and they told me the phone has been block/blacklisted or reported stolen. Besides contacting who sold me the phone, what should I do?

Get your money back. Call the local authorities.

Kinda common sense huh?

I would tell them you need your money back, and tell them you would rather hanle it that way before filing a police report against them for selling you stolen property.

By the way you don't need Wi-Fi to see if its icloud locked, you should be able to just go to erase content and if no icloud ID then it won't ask you for one. The icloud ID also shows in the settings.