A proper app for fixing the missing carrier logo problem in jailbroken and unlocked iPhone 3G/3GS running 3.1.2+ firmware has been released in BigBoss & Planet-iPhones repository on Cydia. Follow the steps below to download and install this app from Cydia inorder to fix this issue.
If you have got an unlocked and jailbroken iPhone 3G or iPhone 3GS running firmware 3.1.2, then you must have noticed by now that the carrier name or logo on the top left side of the status bar is missing. According to Dev-Team, this is caused due to a known bug in ultrasn0w and PwnageTool and it is purely cosmetic, which means your phone works fine even without the carrier logo in place. Follow the steps below to fix this issue.