Cancelling of warranty for own convenience

In 2011 I bought a new Isuzu LDV from Williams Hunt.From then up to now I have hardly used the vehicle to the extent that has it only done 17000 km. I had the initial service of 15000 km done at Williams Hunt but during 2012 also bought a new Chevrolet Utility which I used most of the times.As the vehicle was not really in use and the kilometres so low I did not find it necessary to take it in for the next service.The ignition key is now worn and would not unlock or start the vehicle. I have approached Williams Hunt as the vehicle is basicly still new in terms of mileage and usage. I was then told that the warranty of this vehicle has been cancelled due to inconsistent services.This is a blatant rippoff as the key or ignition of any vehicle is never serviced. It is actually referred to as a non serviceable item. I can not believe that Williams Hunt would revert to these kind of arguments for the sake of R700.