What car was that iPhone paired with?

I've got a 2004 330Ci and a 2004 X5 4.8is which both have problems pairing.

I can pair an iPhone in the normal way and can call up contacts but when I place a call the bluetooth connection drops out when call is connected. Same happens when recieving a call.

I'd love an iPhone and I already use an iPod Touch as the iPhone won't work in my cars.

Can anyone help?