Finally unlock for iPhone OS 3.1.3 05.12.01 baseband is available but not in the way most of you may like. Interestingly an iPhone hardware shop in Istanbul, Turkey has shown a video in which iPhone OS 3.1.3 baseband 05.12.01 is unlocked by reflashing baseband 05.12.01 to 04.26.08. The video shows that initially iPhone has firmware 3.1.3 baseband 05.12.01, later after performing hardware hack the baseband has been downgraded to 04.26.08.
In case you don't know, there is a software method for downgrading 05.12.01 baseband as well, in both cases, either hardware or software, you'll need to go to OS 3.1.2. Step wise instructions given here.
You can go through our step-wise tutorials on jailbreaking iPhone 2G/3G/3GS and iPhone Touch 1G/2G on firmware 3.1.3 using redsn0w 0.9.4, sn0wbreeze, PwnageTool 3.1.5. Unlocking can be done using ultrasn0w or blacksn0w.Contact Us for News Tips, Corrections and Feedback