God does not have to come and tell me what I must do for Him, He brings me into a relationship with Himself where I hear His call and understand what He wants me to do, and I do it out of sheer love to Him... When people say they have had a call to foreign service, or to any particular sphere of work, they mean that their relationship to God has enabled them to realize what they can do for God.
I've been learning a lot about my relationship with God. I'm building it now. Before I seemed to have taken it for granted. I think many of us do!