Through Christ, we have been transferred from the kingdom of darkness to the kingdom of light (Col 1:13).
Though we are in this new kingdom and under this new rule we are still slaves. We are not our own. We were bought with a price (1 Cor 6:20).
We are still slaves. Slaves though, not to sin, but slaves still. We are slaves to righteousness (Romans 6:15-23). You have been set free! Freedom from sin, but slaves still: "But thanks be to God that, though you used to be slaves to sin, you have come to obey from your heart the pattern of teaching that has now claimed your allegiance. You have been set free from sin and have become slaves to righteousness." (Rom 6:16-17).
How will your life reflect the glory of God, as His servant?