What Paul is saying is that we are called by God , we are all one in Jesus Christ, whether when we are called, are circumsised or not, and whether we are slave or not. For when one is called at what state they are in, is not what is important, but having been called by God is what matters that we are free.
Galatians 3:28 "There does not exist among youJew or Greek, slave or freeman, male or female. All are one in Christ Jesus."
Colossians 3:11 "There is no Greek or Jew here, circumcised or uncircumcised, foreigner, Scythian, slave, or freeman. Rather, Christ is everything in all of you."
Yes, I agree, being called by God is important. However, I would add that we answer God's call in a positive manner by the observance of the commandments of God.