After you have jailbroken your iPhone, now you can unlock your 3.1.3 iPhone 3G or 3GS using blacksn0w (with baseband uptill 04.26.08) if your baseband is 05.11.07 click here to learn how to unlock your iPhone, to check your baseband got to Setting=>General=>About and check Modem Firmware if it is below 04.26.08, you can coninue.

If you haven't jailbroken your iPhone, then you need to jailbreak it first before you can unlock. Click here to learn how to jailbreak your iPhone.

iPhone 2G users click here to learn how to jailbreak and unlock their iPhones.

Just follow these simple steps to unlock your iPhone 3G or 3GS after you have jailbroken your iPhone.

1- Launch Cydia on iPhone.

2- Tap Manage.

3- Tap Sources.

4- Tap on Edit.

5- Tap on Add.

6- Enter http://blackra1n.com now tap Add Source.

7- Cydia will update sources.

8- After that tap on Return to Cydia.

9- Tap Done.

10- Now the repositry has been added successfully, search for blackrain and tap it.

11- Tap blacksn0w

12- Now tap Install and then tap on Confirm.

13- When blacksn0w is installed restart your iPhone and voila, your iPhone is unlocked. Enjoy your unlocked iPhone.