Dodgy fuel

My daughter's 2010 Ford Focus has been idling roughly for months, and two weeks ago it broke down. The mechanics at Ford advised that 'poor quality fuel' was to blame as there had been a build up of carbon on the first injector, and they had to get a specialist out to clean it. They also said this was not covered under warranty and charged her $560. With few exceptions my daughter goes to the same service station and only uses unleaded - not E10 unleaded. The Freedom petrol station we use at Indooroopilly asked her to fill out a customer complaint form, which was then faxed to head office. We were told that someone from the company would contact us, but we've just been given the run-around. Is there anything more we can do?