Complain unattended

On the 17th I went to fill petrol at Caltex Redhill, the attendant filled wrong fuel , on my way car gave me problem , I informed the garage I spoke to Naresh who is the manager,he took my details and said will check cameras and will get back to me, he never came back to me I complained on their site ,he phone and asked for a sample, I sent it mind you its a 30 min drive to the garage, he took a picture of my car , I kept calling for feedback he said I must bring invoice from mechanic ,I did after that nothing happened, I kept calling until he told me they won't pay there is no proof because I don't have a slip to prove I used their station. They can only pay me fuel money only . I asked him to send me an email stating all of that he said he will but he never did. I've been calling for 2 weeks now he doesn't take my calls.