cannot unlock htc one x

hi - i have a htc one x locked to orange uk, its totally original phone and never has never been rooted or modded before, i purchased an unlock code and the seller is 100% sure thats its the corrrect unlock code for the phone but it doesnt work, after several times of trying the code it still says " unlock code ir wrong". I also have reset the phone to factory settings and tried with diffrerent sim like gif gaff, vodaphone etc but still remains locked and wont accept the unlock code. I have no reason to doubt the seller. im in the uk. Ive read somewhere that it may have something to do with the radio.zip whatever that is. To be honest im totally new at this modding lark so would be greatful if someone could walk me through this problem or help me in some sort of way. i would like to use my tesco sim in the phone. Thanks

well i got the same unlock code off another seller, so the unlock code is right so why isnt the phone unlocking..? help please