new tyres

I bought a car with not even 50.000 at Auric Auto in Cape Town. When I bought it I have been told that the tires were NEW (that sounded correct to me after 50.000 km). 10 months and 9000 km later the back tyres need to be replaced and it cane out that only 2 tyres were new, but they don't replace for free because I cannot prove that the seller told me that. After Long negotiations I obtained to get the tyres (that cost a real fortune) at cost and guess what?? Now they don't get back to me or return my call in order to let me know when the tyres will be available to be replaced.