The church started in the beginning not on the day of Pentecost. We know that Jesus is the chief cornerstone. This means that the church started when the first stone was laid, that stone was laid in the beginning.
Prophets are also the foundation making it one church.
There is only one church, let us not divide the church as the Trinitarians have divided the Godhead. We also know that Jesus is the rock that followed the children of Israel. There was however two covenants that were made with the church, because of the disobedience of Israel, or the church. Then said he, Lo, I come to do thy will, O God. By the which will we are sanctified through the offering of the body of Jesus Christ once for all.