So I accidentally upgraded my phone to the 4.0 os and after a few days of hell trying how to get the phone out of restore mode and downgrade I finally got 3.1.3 on it. But the thing is that I need the phone to be unlocked. I tried to use a custom IPSW but everytime I do it it gives me error 1015. How can I jailbrek this phone so that I can get Cydia and ultrasn0w back? As well the base band is 5.13.04.