Do not honor the gaurantee

Purchased a compressor. Used it a few times per month. The machine started smoking. I took it back to the store. They promised to get back to me in 3 days with a report. A week later they called to say i need to pay R1000 odd as the machine was over used. I declined to pay and asked for a review. I had to go to the store 3 times as no one replies as they promise to do. Now a month later and still they stand by thier "overuse" policy. Which is ablsolutely untrue.