Some of us are called by God for certain tasks in life. They may be life long pursuits, such as the ministry or charitable service. Or, they may be special tasks such as helping someone through difficult circumstances. It is a mistake to think of "a calling" only in terms of dedicated religious service. God's purpose for us may seem secular or even profane. He often works in mysterious ways.
But what about those who never heard the call? How did they get left out? What are they missing?
Many Christians respond to God's call without ever realizing that it was a call. I tend to think of Christians as "on call" angels, just waiting for the next opportunity to be of service. Following Jesus becomes a way of life, and taking the next step in His direction becomes the natural thing to do. So, acting in His service is nothing new or different, and may not be recognized as responding to a call. Every contact we have with another person provides a new chance to carry His message. Every choice we make in our lives may bring us closer to Him.
In the end, the important thing to remember is that God has called us all to believe in Him, have faith in Him, and worship Him. That is the most important call of all. When we answer that call, all other aspects of living a Christian life fall into place. Yes, we should thank God for the Mother Teresas in the world. But we should never discount the importance of all the ordinary folks living their lives as faithful Christians. A car salesman may dedicate his life to Christ as fully and completely as a priest or charitable care giver. And who is to say that he might not do more good in this world than they?