Hyundai Zambezi tried to **** me R3000!!!

I was scheduled to service my car today at the Hyundai Zambezi dealership. It was a service for my 30 000km. At the moment my km are at 28577km so I took it in early as my last service was last year at these times. I get a call from Hyundai saying that my km's are 38 000km and that I missed my service plan that was for 30 000km so I forfeit my service plan and I need to pay R3000 for a penalty to service my car as I missed my 30 000km. That was not the case when I got to the dealership. I asked for my car back and when I got my car I saw that my km's are actually below 30000km and they are actually 28577km. They tried to **** me R3000 which is unacceptable. They added extra 10000km. How can a whole service company make such a big error. They instited that I must pay R3000. I could've lost R3000 due to such a big ug error. It wasted 2 hours of my work time trying to deal with this matter. I don't recommend anyone to use the service at this dealership. This will be my last time servicing my car there