ok so my old samsung phone did this why cant my iphone

everytime i would get a text message my radio in my car would say i have a new message. i just figured it wasnt compatable.

but recently when 3.0 came out the voice memos and visual voicemail go through the bluetooth sterio in my car.

i have a pioneer AVIC-700BT for a headunit in my car

anyway the question is: Is the headunit at fault or the iphone for not sending the information through.