I, in the past downloaded 3.1.3 from Apple as I thought I had no need for jailbreaking my iPhone 3G. Now I have decided to jailbreak it, I want to use blackra1n as I know it works on 3.1.2 but not on 3.1.3. I would not like to use any other type of jailbreak as I'm sticking to blackra1n. Is there anyway to downgrade my firmware as I need to do it soon I'm stuck. P.S : I don't need to unlock the phone.