There WERE only those listed in the bible and none today. The 12, then Mathias added to replace Judas, and then Saul (Paul) called by the Lord. That's it. No more.
You have a problem with limiting apostles to those when there are any others the Bible names apostles, as was Barnabas, who was leading Saul who was also known as Paul (that was not a change of name, he had both names that were his), Acts 14:14.