The safest and easiest way to unlock an iPhone is to unlock uisng remote unlocking service. I have unlocked my iPhone using this service. You too can try with this service to unlock your iPhone 4. This method of unlocking is safe, simple, affordable and quick. You can get the remote unlocking service for an iPhone 4 from (MODERATOR EDIT: No external links) at low cost with easy step by step unlocking instructions. This methodm of unlocking doesn't require a jailbreak too. All the best mate.