American Leak Detection Charged me $175 for second visit under warranty Thousand Oaks, California

Company Representative advised me to have him return within 30 days for follow up visit to retest equipment. He promised no charge but now the company is charging me $175. No where was it mentioned that this charge existed. With good faith I had my equipment repaired, but not to the standards of the company. Now I still have the same problem as before & have already paid them $300. Now they want $175 more but the problem still exists. I had 2 professionals look at my problem after the first service & they stated that there was no way my problem was from the condition of my return line. I have since fixed the small leak they claim caused the original problem yet my pool level still drops, confirming my conclusion. I am outraged that they are insisting on charging me $175 for return visit that lasted 10 minutes & didn't solve a thing.