Why would not want it to auto-pair? There has to be a setting on the phone no still notify you when paired up. Mine does. I can't imagine being easier to pair up the phone to answer it rather than just having it be paired up every time.
If you still rather not have it paired up, go through the menus on the car and see if there's an auto-connect option as well. I vaguely remember something like that on the car settings. The tip given above is to turn off bluetooth audio, not to avoid BT pairing of the device.