Does not stay near estimate and will take your stuff if you disagree

I had my older craftsmen lawn tractor picked up to be repaired I was given a verbal estimate of $400-$500. 3 Weeks later I was told my lawn tractor was ready but the bill was $697.93. I complained that the bill was much higher then what I was told and I was not consulted before the work was done and this is the response I got "You were told up to $500 for a new deck shell and to swap parts over. Neil warned you that the spindle assemblies may break when swapping and that they may need to be replaced as well. Did you think there would be no tax on it? You are in Canada.There is tax. That is right in line with whet you were told. If you failed to listen I can not help that." I refused to pay the bill and he has kept my lawn tractor to sell so he can recover his costs. Clearly has no respect for his customers and I would take my business anywhere else.