I buy a blocked iphone 3GS ... how can i unblocked it?

I buy an iphone 3gs from my freind but the ph is blocked so no one want to unblock it in uk because its not right to unblock a blocked ph ..... they told me they might unlock it so that i can use any sim with that iphone but because its blocked so they can not do any thing to it .and now my freind refuse to give my money back because he already mention me its blocked but i didn't realise locked and blocked is two different thing. if you can please help me to unblocked the iphone please.