This isn't good news for all users based on the SAM unlock solution, but the good thing is that not all users have lost the possibility to unlock their iPhone 4 / 4S.
All users who were proactive to unlock their iPhone 4 / 4S using Loktar_Sun's SAM tool, backed up their unlock activation tickets can still restore those unlock tickets and unlock their iPhone 4 / 4S. If your iPhone is already unlocked using SAM unlock tool, immediately you must Backup your unlock activation ticket before it can be too late.
Remember that you'll still need a jailbroken iPhone 4 / 4S to complete this, and you should need your backed up Lockdown folder.
Restore SAM Unlock Activation ticket to get your iPhone 4 / 4S unlocked:
Be aware: This guide assumes your have your backed up Lockdown directory available on DropBox.
Step 1: At the start insert the Unofficial SIM card for which you backed up unlock activation ticket.
Step 2: Now open iFile and go to /var/root/Library. Press edit in the upper right corner, and choose Lockdown, and press the zip button backup up the existing Lockdown folder. The name will be something unique. Go to the bottom to make sure that a backup *zip file is created. Then remove the Lockdown folder.
Step 3: Now open DropBox, find your copiedLockdown folder with the valid unlock activation ticket from the unofficial Sim. Open the *zip file with iFile, and choose Unarchiver. Your Lockdown folder will be unzipped.
Step 4: In this step Press edit in the right corner and select LockDown, and copy the LockDown folder.
Step 5: Now Navigate to /var/root/Library, and press edit, and paste the LockDown folder.
Step 6: Should you still have SAMPrefs installed, go to /User/Library/Preferences, search for SAM, now delete the com.bingner.sam.plist file. Now Power Off your iPhone.
Step 7: Now Power On your iPhone, wait for a minute once it gets to your home screen, and finally your carrier should now will show the carrier from your unofficial SIM.
If you encounter any error let us know in the Comment section below.