XT912 is for Verizon and it has only cdma band enabled in it and the best is that is not locked;
When you insert a nonVerizon sim card you get the message:
"This SIM card is from an unknown source!"
To make it work just download Radiocomm 11.12.2 from here:
RadioComm_v11.12.2_Install.zip , after this connect the phone to the pc and select pc mode.
In radiocomm go to ma/common/mdm 6x00
go to settings/usb/pst usb drivers
switch to ftm common 1 and wait for the phone to make it purple or green
on the upper side in NVAcces got to value 1877 NV_RF_BC_CONFIG_I
Read the value from the device and after that replace first 16 digits with:
8703E804000200
write data back and restart.
Insert an gsm card into the phone and the gsm band will be enabled
The solution that I explained here already is posted on xda forum; all the credits go to them
I just only apply it with succes on several xt912.
Regards!