Unhappy client

We have a Ford Figo Ambiente 2013. We took the car for it's 40 000km service to Lazarus Ford Malmesbury. We mentioned to the service dept that the fuel gauge is not working like it should. When we full up the tank with petrol after 20km the gauge dropped to the three quarter mark. They told is they did fixed it. Every service we complain about the same problem they even book the car in for 3 days to "repair " the problem with the gauge. As you know after 4 years or 120 000km the new vehicle warranty you not benefits from the warranty. Well the petrol gauge problem is know even worst than every. With every service we complain about the petrol gauge know if this gauge have to be replaced we have to pay for it because Lazarus Ford will tell us the new vehicle warranty had expired. Unhappy with the service of Lazarus Ford.