Bought unlocked Iphone 5 from CL, 5 months later phone is blocked?

I bought an unlocked Iphone 5 from someone off of craig's list roughly 5 months ago and I found out today that the phone has been blocked by T-mobile and I'm unable to make any calls because apparently the person who I bought the phone off of did not fulfill his contract obligations. I paid $420 for the phone and now I have a very expensive ipod and I'm pretty devastated. I'd like to know whether the Iphone still has value or if i should try and sell it internationally? Or if there's a way to use it for AT&T since T-mobile applied the IMEI block? Any help would be appreciated.

Scrap the the iphone and buy an android.