Unlock Sim without code

[mazz158]

I have a Samsung Galaxy S2 my phone has been messed around with over time (ie somebody in China managed to make my phone sim free, i dont know how?) but now I'm back in UK and have been trying desperately to get my phone sim free, myself.. It seems to me that the phone requires it to be rooted, I am a beginner newbie to how to do this, and have tried hard to finding info how to do this (make sim free).. My phone was originally with 3 network in UK My phone is now rooted (Cynamod), i have tried various apps online which claim to unlock phones but with no luck. the phone does not ask for any codes when i start the phone, only that when i try to make a call the phone says i'm not registered to the network, I have tried to placed the sim card in another phone, and the sim card worked fine? When i have read about various codes online to input numbers into the phone keypad for information about the phone e.g NOT REAL CODE(*#54646#) My phone does nothing!!!( although i can recall the IMEA number!!!!! But this number does not match the IMEA number which is behind the battery in the phone!!!! When rooting my phone i think i saw a folder called "efs backup" is this the problem or answer to my problem??? I dont know what this does? But I'm guessing it may have something to do with solving my problem......Please Please if someone could help me with this, it would be a life saver i cannot affor to buy another phone at this point, and just want my GS2 to work correctly, thank you so much for any help and advise you can give!!