Nissan - *****ed out of 90000 service plan

I am a very dissatisfied customer. In September 2016 I went to look at Nash Nissan to buy a brand new Nissan Almera as they were advertising a 3 year 90 000 00 service plan on the car. I currently do 30 000 km a year travelling to work and back so would never settle for a 60 000 km service plan as I know this would be depleted in 2 years. After test driving one I went to the Sales agent (Sean Naested) and sat in his office and signed a document (which I assume was a offer to purchase). On this document I noticed that it said 60 000 km service plan and questioned him about this. He then with his pen crossed out the 60 000 and replaced it with 90 000 kn service. I recently found out that I am only now covered for a 60 000 km service plan. A few month's ago I got hold of Sean to query him about this and he denies knowing antything about it and said he would need to find the paperwork. I then followed up with him twice after that and he came back saying that they (conveniently) could not find this paperwork. I then took the matter to the Dealer Principal who said that he would inquire and come back to me. It has now been a few months now and he has not had the decency to come back to me. As far as I am concerned ALL of my paperwork should be in their care. I know the deal I had with the dealership. Whether it was the fact that I am a single lady who they think they can mess with, I don't know. All I do know is that if they do not have the integrity to honor deals made then I will never buy another Nissan again and will also discourage anybody I know never to buy one either