I reckon this is something that you should so if you’ve been naughty and you have a jailbroken iPhone.  if you fear your iPhone 4 IMEI could be banned…there’s a way to prevent the worse from happening. SAMPrefs is available on Cydia and it will allow you to backup your activation for future (if needed) restoration of your IMEI. I assume your iPhone is jailbroken.

• Launch Cydia, click Manage on the bottom menu bar. Then click on Sources and tap EDIT and ADD. Add this to the repo http://www.repo.bingner.com

• Once Cydia has refreshed the sources, go to Search on the bottom and type: SAM and install. Two apps will be installed SAMPrefs and SAM.

 

• After installation is done and Cydia refreshed, you’ll see a new SIM icon on your springboard. Tap on it, go to Utilities and Backup Activation. If in the future something happens, open it again and Restore Activation.