I have an iphone 3gs which i accidentally upgraded to 3.1.3. So now if have 05.12.01 boot rom. I used itunes to downgrade to 3.1.2 with my cydia shsh. It gave me an error 1015 but it did the restore. My phone is now 3.1.2 with 05.12.01 boot rom. I ran the blackrain jailbreak and my phone was jailbroken but I have no carrier signal. I also ran the blacksnow unlock and still have no signal. I have an att sim card. How can i fix this problem?