It's been said by many that Neville couldn't have phoned the police because of his injuries. He could still have just dialled 999,without speaking as that call would have appeared on a digitalised screen showing the area/address rather than having the loud distracting buzzer. The address of the caller would have been recorded and filtered to the police as being the emergency needed if " suspicious sounds " had been heard in the background.
This occurs if a line has been dialled then abandoned and left open for the emergency services.