If you got iPhone OS 3.1.3 with baseband 05.11.07 we have good news. MSFTGuy and Push Fix dev have created and released a modified version of BlackSn0w, that’s able to unlock iPhones with OS 3.1.3 and Baseband 05.11.07.

It is still in beta mode and includes some bugs, but if you are not afraid you can download the beta via repo http://cydia.pushfix.info/. Remember this patch is only for iPhone 3G / 3GS users with baseband 05.11.07 only.

Source [FSM]