Your navigation device like Bluetooth devices or GPS must be paired with the iPhone before use. Follow these steps to pair your device with the iPhone.
1. Make sure the device is set up to be discoverable or to search for other devices.
2. On the iPhone, choose Settings -> General -> Bluetooth -> ON
3. Choose the device and enter the PIN number or pass word for the device.
4. The device is paired with the iPhone.
You must connect the headset or car kit with the iPhone to use the Bluetooth device for calling. You can get more information by following the instruction came with your headset or car kit to connect to the iPhone. If you will still get problem go to any auto repair center
they will fix the problem.