yeah, unexpected passing like this case sometimes lead the soul to think they are still alive; using the phone was his way of letting his family know. If they tried to use some listening frequency kit like the ghost hunter use, who knows they may have heard him. What appears crazy to us is not unusual phenomena. Some spirits stay on Earth, wander around unaware of their passing and sometimes they know they passed but could not let go. It is important to help them pass through especially with the family. Sometimes the family can cause the passing soul to stay if they feel that the people they left behind will struggle as a result of their passing.  In itself, it is a lesson for the soul to let go and for the family too. 😔