iPhone not working with 'unlocked' iphone HELP PLEASE!!

Hi there,

I have recently been given an iphone 5 by my friend. The new iphone is/was locked to EE, so my friend rang them up to unlock the device. He then received an email a few days later explaining the procedure to complete the unlocking (Restore, plug into itunes etc). I am currently on THREE and had to order a new sim card as my current one does not fit. When the new one arrived, I activated it online, and have tried restoring the iphone, plugging into itues, etc etc and i am STILL getting the 'Sim not valid' error every time.

I got my friend to ring up EE again and they said it was unlocked and to follow the process again, which had no improvements. I have since then noticed that now when I enter the new THREE sim card, the signal bars show on the top of the screen with 3G (No service provider shown though) But still get the SIM NOT VALID error. Then I took the sim out, looked on the iPhone settings, and under Carrier, it say 'Three UK'. This to me sounds as if the phone must be unlocked to say that when before it always said EE. However, the sim does still not seem to work in the phone or on iTunes.

Could somebody please help as I activated the THREE sim card as instructed by EE from my fried, which then deactivated the sim in my old phone. This now means I dont have a working phone between the 2 because the new activated one doesnt seem to work with the iPhone.

Any help is much appreciated, thanks.