Grandstream Shows name of who you are calling


I have around 50 grandstream 2000 phones setup now on my asterisk system and compaired to our old phone system People have pointed out the following problem which im not sure how to sort it.

Say i have 3 extensions 100=nick 101=tom 102=david

On the old norstar system if im nick and I call ext 101 my old phone would show ‘CALLING Tom’ on the display.

On the Grandstream phone when I dial 101 all the phone shows on the screen is 101 and not the name.

Does anyone know a way around this. ?

my sip config is like

callerid=Tom <101>

On incomming calls we have a program on our pcs to do a lookup for the clid. using the manager interface which works ok