ryobi refuses pay back money on repair that did not happen

i have a ryobi lawn mower and it engine was leaking oil. it was under warranty and i went in for repair. Erick Bezuidenhout say it has dust in the engine that's why it leaks oil. He i must pay R800 for the repair. and then after a few phone calls he come down to R400 i paid for it. the second time i started it it was doing it again. i took it in again and ask for my money back. He said its because there was dust on the air filter. that's why it runs on choke. So to him i must not cut grass because there is dust in so what must i cut then? They refunded me on the lawn mower but revues to pay back my money for the repair that did not happen.