unreliable and bad service

I took my vehicle to Edenvale Supa Quick to have the catalytic converters chemically cleaned and replaced. Even after they examined the vehicle, they did not see there where 4 catalytic converters so when I gave them the go-ahead they realized they then realized this. So instead of removing, cleaning, and replacing all catalytic converters the only cleaned 2 and reamed out the other 2. In doing so damaged the exhaust sensor. After complaining and charging me an additional R1200 the sensor is still damaged and they have removed all the vehicle catalytic converters. I have complained to there head off yet almost a year later still nothing is being done to resolve their mess. Their work is professional and all they seem to be good at is making excuses. Even complaints to the head office get you nowhere!