I would Say that God Choses them By if they Are For one Have Study to Show themselves Approved Unto God, 2. which should be First Holy Ghost Filled and Annoited By God. I feel that God Calls Them But He Lets them Know When they Are Ready. There Is a Difference Chosen, and Called Then Called , and Ready. Also if they Have killed the Flesh Mortified it, and thats Daily, and the Heart must Be Clean