Incoming calls on my new Iphone 5 are not directed to car bluetooth system as should be while all other functions operates well

Incoming calls are not directed to my car bluetooth system as should be while all other functions of the bluetooth operate well with my car system.

I tried another Iphone 4 with i.o.s 6.0.1 and all functions worked well. I assume it is a problem of i.o.s 6.0.2 .

How do i solve that