Someone sold me an iphone that is locked? What can i do?

I bought this iphone 4 from someone on CL and he claimed it was at&t Unlocked. I met with him, looked at the phone, seemed nice.paid and everything and we left. I tried my T-mobile Sim and it doesn't work on the phone. Contacted him but he wouldn't answer… I called at&t to unlock it but they want the phone number registered on it and the 1st and last name. What can i do? Can i threaten to sue him for my money back? I have his phone number and license plate.

Sadly you fell for the CL 'great deal' trick. Likely the phone is reported lost/stolen and you were ripped off. Many end up on CL. The rest eventually make it overseas on the black market. There really aren't any options. Can't sue. You don't even know the guy, don't have a receipt or a contract drawn up. He won't even call you. Can't file a police report. You are technically is the possession of probable stolen merchandise. ATT won't unock without that information. If it iCloud locked maybe you can find the Apple ID email or the original owner and offer to pay them to have it released. But you'll still be unlock fees IF the serial number hasn't been fried due to theft. Bottom line; it's a paperweight. Resell to someone that will pump it overseas and don't fall for the iPhone great deals on CL. Lesson learned. Best luck.

Not much you can do after the fact when you have been scammed. In the future ALWAYS ask for the phone's IMEI or ESN, and check with the cell phone carrier, or an online IMEI/ESN checker, before money changes hands, if the seller tells you no, walk from the deal, no matter how good it seems.

As you found out, if you are not the current owner of the phone with a active At&t account, you will not be getting them to unlock the phone. You can pay an unlocking service to unlock the phone, but after doing so, when you try to activate it on your cell phone carrier, they are going to ask you for the IMEI number on the phone, to verify that it has not been reported lost, stolen, or being financed. And if it turns out it is one of those issues, they will basically tell you, they can't activate that phone, until the issue has been cleared up.

In the case of it being a lost or stolen phone, the original owner MIGHT help you with that, but it's unlikely, considering you will have to hope that At&t will contact the original owner and have them contact you.

If it was being financed, the owner will have skipped out on their phone service/contract/paying off the phone. And the likelihood of them coming forward NOW, to pay things off are a snow balls chance, in a blast furnace, at high noon, in the desert.