The only thing you can really do is ask the guy you got it off to give you the code. If he dosn't know it, or can't remember, you have a right to send it back. If he refuses, then take legal action against him - you bought it for a price didn't you? It wasn't described as locked was it? So therefore you have the power to correct the situation. Try consulting Ebay or something. Or you can somehow convince the phones provider (if you know which one it is that is) and ask them to use their "intelligence" to get it unlocked. I dunno but flashing might give you a second shot too.