If it says you are not allowed to unlock the bootloader then unfortunately you can't unlock it..
Nokia 5233 (At home)
Nokia 5230 (Broken Display)
Sony Xperia L (Stock 4.2.2, Rooted, ThunderZap 3.1-Lite)
Ex-Symbian Modder, new to Android world
Hit "THANKS" button, I appreciate it..