You can't unlock your iPhone 3G without jailbreaking. You need to jailbreak your iPhone for all methods of unlocking. The safest method among them is to unlock through remote unlocking method. You can get the remote unlocking for your iPhone from www.unlocking4u.com this is also an affordable mthod too. This unlocking process is very simple and easier. You will get complete guidance on unlocking process. All the best mate.