Pairing Blackberry with Ford Audio

[glider]

Apologies if this has been covered elsewhere.

I've recently got a Blackberry Pearl and whilst I can pair it with the Ford Audio bluetooth in my car no problem, when I make or receive calls it doesn't do it through the bluetooth in the car but just through the phone as normal.

I've also got a Nokia phone which works fine with the bluetooth in the car as did my old motorola.

Has anyone got any suggestions please?

Thanks.