Bad customer service at Hyundai Lenasia

When I bought my pre owned car, I was told it goes for an annual service and that my next service is in January 2020. Now I'm told that I have to pay R4200 because my Kilo meters are over by 7k while I'm on service plan. I was only advised to service the car in January and I was not advised at how many kilo meters. Hyundai service is very poor