Engen Petroleum put wrong fuel in a diesel Car

We log a complaint about the Engen Petroleum in Olifantshoek, after that Engen head office contact me and then I explain to the lady and she agree with us about the petrol that the Engen worker put in our Diesel car and my whole Engine from my car is damage but they tell us they have insurance for that know they send only a email that the problem is resolved but I don't accept it