I thinkk one can see why there are different titles among the denominations just by the differences in opinion and interpretation in this thread. There are some churchs that use the title apostle while other churchs don't use it as a title. My church doesn't use the title because the Bible gives evidence that the number of apostles (12) was fixed. Matt. 19:28
Jesus said to them, "Amen, I say to you that you who have followed me, in the new age, when the Son of Man is seated on his throne of glory, will yourselves sit on twelve thrones, judging the twelve tribes of Israel.
Rev. 21:14
The wall of the city had twelve courses of stones as its foundation, on which were inscribed the twelve names of the twelve apostles 11 of the Lamb.
This is probably why the title isn't used in some denominations. IMO some churches look at it this way. The Bible has been written, there hasn't been anything added to it. Which makes it the definite word of God. Jesus and the Apostles did their job of spreading the gospel and creating the church. Bishops (elders) and deacons were left behind to do thier respective duties. Thus the titles of bishop and deacon are used today, while the apostle title has been reserved for the 12 that followed Jesus Christ.
Those churchs who are not of the episcopalian structure do sometimes use the apostle title and use it synonomously to the Bishop or Elder title. I would think that the rational behind using the title is from the Greek meaning of the word apostle "to send" or to preach or give the Word of God.
This thread has been very enlightening for me. I have learned a lot from everything that was said.
Remember, dont' get caught up in who's right and who's wrong because we don't know. It's all about interpretations and beliefs on the church government structure. As long as we all know there is only One God who had only One son who gave his life for our sins, and that there are many forms of church government which we should all respect we all we be just fine.
God Bless!