After you have jailbroken the iPhone firmware 3.1, you will discover there is no carrier logo (pictured above on the left). In the settings, it can’t display the carrier you are using. But, the phone functions actually still work. You can still call your friends and get online. Hence, it would be only a cosmetic issue.

If you feel uncomfortable and just want the carrier logo, you can try to install the MakeItMine freeware from Cydia. Type the name of the carrier you are using, and click “Carrier” at the top left. Quit the app and you will have the carrier text.(pictured above on the right) I know it does not really solve the problem, and the text won’t change after you switch the SIM card, but it actually looks better than nothing. Right?