beginning from the baptism of John until the day when he was taken up from us—one of these men must become with us a witness to his resurrection.” 23 And they put forward two, Joseph called Barsabbas, who was also called Justus, and Matthias. 24 And they prayed and said, “You, Lord, who know the hearts of all, show which one of these two you have chosen 25 to take the place in this ministry and apostleship from which Judas turned aside to go to his own place.” 26 And they cast lots for them, and the lot fell on Matthias, and he was numbered with the eleven apostles.
For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures, 4 that he was buried, that he was raised on the third day in accordance with the Scriptures, 5 and that he appeared to Cephas, then to the twelve. 6 Then he appeared to more than five hundred brothers at one time, most of whom are still alive, though some have fallen asleep. 7 Then he appeared to James, then to all the apostles. 8 Last of all, as to one untimely born, he appeared also to me. 9 For I am the least of the apostles, unworthy to be called an apostle, because I persecuted the church of God. 10 But by the grace of God I am what I am, and his grace toward me was not in vain. On the contrary, I worked harder than any of them, though it was not I, but the grace of God that is with me. 11 Whether then it was I or they, so we preach and so you believed.
Two important points to understand here. First, Apostles were designated by those who were personal witness of the resurrection and were assigned to the specific task of proclaiming the Gospel, as Acts 1 makes clear in the text above. Second, Paul makes it very clear that he was "last of all" assigned to be an Apostle as one "untimely born." In other words, Paul was an unusual case because he was not a part of Christ's earthly ministry nor did he witness the resurrection. Rather, he became an Apostle via special revelation as one who became an Apostle in a very unique way. Moreover, Paul speaks of Apostles as the "foundation" of the church. The foundation has already been laid through the preaching of the Gospel by the first Apostles. That was their role. Apostles laid the foundation for the church. Thus, there are no Apostles today because 1) the original witnesses died and 2) the foundation of the Gospel which was fully proclaimed has already been laid. Apostles were specifically called to proclaim the unknown message of Christ to the world. Paul testifies to this in almost every letter as he declares himself to have been "called" by Christ himself as an Apostle. An Apostle is far more than someone that is merely a believer. Otherwise, Paul would not have made such a big deal in his position as an Apostle in the letters he wrote. He started those letters proclaiming he was an Apostle as a way of telling his audience that he was specifically chosen and sent by God to proclaim a message that had been personally revealed to him. So if Jesus has not personally revealed himself to you and has given you a message previously unknown from ages past...then you are NOT an Apostle.