God is not a slave owner. He has servants who choose to serve Him out of love, but never is God a slave owner.
Luk_12:4 And I say unto you my friends, Be not afraid of them that kill the body, and after that have no more that they can do.
Joh_15:13 Greater love hath no man than this, that a man lay down his life for his friends.
Joh_15:14 Ye are my friends, if ye do whatsoever I command you.
Joh_15:15 Henceforth I call you not servants; for the servant knoweth not what his lord doeth: but I have called you friends; for all things that I have heard of my Father I have made known unto you.
Abraham is the friend of God:
2Ch_20:7 Art not thou our God, who didst drive out the inhabitants of this land before thy people Israel, and gavest it to the seed of Abraham thy friend for ever?
Isa_41:8 But thou, Israel, art my servant, Jacob whom I have chosen, the seed of Abraham my friend.
Jas_2:23 And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God.
Moses is the friend of God:
Exo_33:11 And the LORD spake unto Moses face to face, as a man speaketh unto his friend. And he turned again into the camp: but his servant Joshua, the son of Nun, a young man, departed not out of the tabernacle.
John the Baptist, the friend of God:
Joh_3:29 He that hath the bride is the bridegroom: but the friend of the bridegroom, which standeth and heareth him, rejoiceth greatly because of the bridegroom's voice: this my joy therefore is fulfilled.
Lazarus God's friend:
Joh_11:11 These things said he: and after that he saith unto them, Our friend Lazarus sleepeth; but I go, that I may awake him out of sleep.
God's friends:
Zec_13:6 And one shall say unto him, What are these wounds in thine hands? Then he shall answer, Those with which I was wounded in the house of my friends.
God brings people out of slavery:
Exo 20:2 I am the LORD thy God, which have brought thee out of the land of Egypt, out of the house of bondage.
Joh_8:32 And ye shall know the truth, and the truth shall make you free.
To be called a "slave" is to not be free. It means you are still the slave of the WTS, satan, sin and selfishness. Christ Jesus died to set you free.