In both New Testament lists of the ministry gifts, the office of apostle is listed first, indicating that it is the highest calling (see Eph. 4:11; 1 Cor. 12:28).
No one begins his ministry as an apostle. A person may be called to be an apostle eventually , but he won’t start out in that office. He must first prove himself to be faithful over a period of years in preaching and teaching, then, eventually, he will stand in the office God has prepared for him. Paul was called from his mother’s womb to be an apostle, but he spent many years in fulltime ministry before he finally stood in that office (see Gal. 1:15-2:1). He actually began as a teacher and a prophet (see Acts 13:1-2), and was later promoted to be an apostle when he was sent out by the Holy Spirit (see Acts 14:14).
We find mention of other apostles besides Paul and the original twelve in Acts 1:15-26; 14:14; Rom. 16:7; 2 Cor. 8:23; Gal. 1:17-19; Phil. 2:25 and 1 Thes. 1:1 with 2:6. (The word translated messenger in 2 Cor. 8:23 and Phil. 2:25 is the Greek word apostolos. ) This dispels the theory that the apostolic office was limited to only twelve men.
Only twelve apostles, however, can be classified as “Apostles of the Lamb,” and only those twelve will have a special place in the millennial reign of Christ (see Matt. 19:28; Rev. 21:14). We no longer need apostles like Peter, James and John who were uniquely inspired to write Scripture, because the Bible revelation is complete. Today, however, we still need apostles who establish churches by the power of the Holy spirit, just as Paul and other apostles did, as described in the book of Acts.