Service not approved - employee giving wrong info

My car was due for a yearly service in October 2015, as it was serviced in October 2014. The km it was serviced on was 74000km. When I phoned to book the service the lady told me that I cannot service it yet as the service plan won't cover it, as it is not yet 10000km after the previous service. The car was then on 82000km. I had to drive it untill 85000km before it can be serviced as a yearly service. I booked my service for today on 85000km. It was declined because I didn't bring it within the prescribed 11-14 months after previous service. The current staff at Hyundai are unwilling to assist due to the fact that I have no proof that the conversation took place, and they cannot help me any further. This is poor customer service, as I feel that the client comes first. And if their staff were not properly trained it is not the customer's fault. I sincerely hope other people who have issues with Hyundai Witbank can also comment, as I am at a point where I would rather sell my car and deal with another company that is willing to walk the extra mile for the customer.