My range/oven was not working immediately after I bought it. I had a repairman come out to inspect it. He declared it my fault due to too much...

...incoming voltage and charged me even though I was under warranty. I had it double checked by the power company and an electrician who said the oven was faulty. The oven company provided a new oven which has not had any issues. I''d like my money back and I''m worried this company is lying and stealing from others as well. If they refuse to return my money, what can I do?