Change IMEI number

I was trying to unlock the bootloader on a sony xperia z5 but its perma-locked by the carrier so that plan went out the window
so I'm Wondering can I still root the device and also change the IMEI number or does the device bootloader have to be unlocked

And if it can be rooted whats the best way and is there any guides on doing so

Ok Ive check the links in forum http://ift.tt/1OvPaXX which has great info

and according to the guides if the bootloader is carrier locked you cant root it or change anything its game over !!!!!

from xda-developers http://ift.tt/1Qz7aC7
via IFTTT