Frustrated customer

I bought a 2018 Hyundai I20 in May of 2020 as a first time car buyer at Hyundai Bryanston , and the car had 41 000km on it. In September of the same year I took the car for a 45k service at the same dealership and it was done. Now I wanted to do a 60000km service and I am told that the service would actually be for 75000km and not 60, this is because the 45000km was done at 40000km according to their records, I WAS NOT INFORMED OF THIS. This 40k service was done 8 months after the 30000km was done and I was not informed of this. I was sold this car and given and impression that my service plan was for 36 months (45, 60 and 75) but now I am told that it is actually for (60, 75 and 90). I was not fully informed and there was absolutely no transparency from the dealer. Furthermore the service book which I was given was not stamped nor was it completed after the 30k service and I only realised this in September 2020 when I took the car for what I had assumed was for 45k service and it was only stamped then indicating that the 40000km was done. The incomplete service book meant I had no way of knowing the full service record of the car. The inaccuracy and non disclosure of this information infringed on my right to know the full information of the product before I bought it.