Galaxy S2 Bluetooth connection

I have just purchased a Citroen (C5 2011). While my Nokia X3-02 has no trouble synching with the car's Bluetooth system, the Galaxy S2 does. When the Nokia synchs, I can access all my contacts in the phone by using the vehicle's controls and screen. However while the Galaxy synchs with the Bluetooth system, it shows it's connected and I can receive and make calls, but I have to do this using the phone, after which the connection works ok and is hands-free. Is there some setting in the Galaxy S2 that I need to make so that I can make and receive phone calls using the Bluetooth system in the Vehicle. As I say, the little ol' Nokia works just fine. Why won't the S2?