If a car falls into the water, it's important to act quickly. A car weighing perhaps two tons can generate enormous force when it hits the water.
The first thing you have to do is survive the impact without hitting your head and becoming unconscious. The best way out is always through the side windows or the sunroof. Making a phone call is just wasting valuable time. In most cases, a rescue team would not be on site in time anyway. The electronics should continue to function for a short time even if water has already entered.