Press *#06# on keypad.
Eject the sim tray. The IMEI will be printed on the sim tray
Use Any Network : Freedom to use networks anywhere in the world,simply by changing your SIM card.
Avoid Roaming Charges : Avoid roaming fees when traveling.
No Risk : UK O2 iPhone 4 Unlocking Service do not damage your phone in any way.
Permanent Unlocking : Once UK O2 iPhone 4 cell phone is unlocked it will not re-lock itself.
Technical Knowledge : No Technical skills or knowledge required.