Overcharged service

I recently had Plumbing Johanesburg come to my home to do leak detection tests. On consulting them they described various sophisticated means which they use to detect leaks, namely gas injection into the pipes. They came, walked around my property and prescribed that a leaky toilet and sprinkler was at fault. Therafter they billed us for R1300. I disputed the bill on grounds that no gas leak detection was done. They conceded they would come fix the toilet and only charge for parts. After the job was done I received yet another bill for R1200. Therefore we effectively paid R2500 to fix one leaking toilet.