UK O2 iPhones Official Unlocking
IMEI based permanent sim unlock for iPhone locked to United Kingdom O2. iPhones 3G/3GS/4/4S, all basebands and firmware covered.
Official Apple iTunes Unlock - warranty remains valid
Permanent - always upgrade to the latest version of iOS
No need to run any complicated software. Once you have made your purchase, simply connect your iPhone to iTunes to complete the unlock.