Dishonesty and Bad service..

I bought a used car I'm March and upon taking delivery I was told that the vehicle was fully serviced and will only require service either at 75000km or March n 2022 ext year or whatever comes first. The shock I got when took I took the vehicle for service today at 75000km and was told the vehicle was long due for service in May and I had to pay for the service. I called the dealer Hyundai Weltervreden where I bought the vehicle and was told we cannot acknowledge we made a mistake however you will need to pay for the service.. What nonsense is that..