I think, it is described in 3. post -> Frankenstein section.
Dial the following code into your phone:
*#272*IMEI# (while IMEI is the IMEI of your phone)
If you have a multi CSC, there will be a list of available CSCs.
Just choose the one you want.
Be careful, because this will wipe your phone.
Backup can help.
Sent from my GT-I9100 using XDA App