Paul did not just decide to become a Christian and then an apostle. He had an encounter that convinced him of Christ Jesus as the Truth. He earnestly sought out other Christians and was Baptised with the HolySpirit.

He was then led by the Spirit to Arabia where he was taught the Gospel of GraceThroughFaith. Upon getting that revelation he returned to Judea and met with the Christian leadershiip and began the ministry that the Lord Jesus had given him - to the gentiles. So, Paul humbled himself to the calling of the Lord who raised him up to apostleship,

Here Paul acknowledges -> the physical part of the BodyOfGod
!sp9 1) shed blood
!sp9 2) resurrection
!sp9 3) Damascus vision -> the verbal part of the SoulOfGod
!sp9 1) teaching
!sp9 2) revelation -> the spiritual part of the SpiritOfGod
!sp9 1) NewBirth
!sp9 2) leading
that the SpiritSoulAndBody played in His calling and preparation.

This is one God who now manifests -> as SpiritSoulAndBody -> in our LordJesusChrist.