Reconciling religion with Master/slave relationships
The question: "The bible says 'Call no man Master'"
"How do you handle that in your Master/slave relationships?"
I first need to put your rough biblical quote into context. In the King James translation of the bible the word 'master' or 'Master' appears over 150 times in the new and old testaments. Each time 'master' is used in translation, it is of course the word chosen by the translators to represent some underlying Greek, Aramaic, or Hebrew word form the original manuscripts. There are actually twelve different words in the manuscripts which were translated as 'master' or 'Master', ...
In the case of your quote, I believe you are referring to the book of Matthew, Chapter 23, Verse 10 which states, "Neither be ye called masters: for one is your Master, even Christ."
Christ spoke those words to the Pharisees in reference to their leading the Jewish people away from God. The original Greek word was 'kathaygayface.' 'kathaygayface' appears only two times in the bible and the book of Matthew contains those two occurrences. The word 'kathaygayface' does not appear anywhere else in the original manuscripts and it does not refer to Master as we know the word, but to Rabbi, see below.
That same Greek word (kathaygayface) appears two verses prior in Matthew 23:8 as Rabbi. Matthew 23:8 "But be not ye called Rabbi: for one is your Master, even Christ; and all ye are brethren."
These words from both verses, spoken by Jesus, were directed specifically at the Pharisees in reference to their leading the people away from God; his admonition had nothing to do with the word 'master' specifically, nor with the concept of calling one's owner Master. He was simply saying to the Pharisees that they should not want the people to think of them as equal to God, and their false rabbinical teachings were not to be put on a level with God's word.
Therefore, there is no conflict between a slave, even as we mean the word slave, calling her owner 'Master' as long as she does not worship him as a deity nor think of him as Master in the sense that Christ is Master.
If you are a Christian slave and are looking for a Master then you had better be careful to find a Christian Master who can also be your spiritual leader, otherwise you risk being drawn away from your relationship with God.