Help!! taking an english mobile out to Turkey 4 a friend??

Hey all just wondering what the situation is if you want to take an english phone out to Turkey and put a Turkish sim in it??? I want to take a phone for my friend but I know that in bout 1 / 2 weeks it will be cut off in Turkey?? Does anyone know how I can make it so this does not happen?? I dd here once that you should register it at customs, but im not sure how this works and would be greatful for anyones help!!!!!!!!
If not does anyone know how much it will cost me in Turkey to sort this out?? Thanks Loads 

