I've sent them proof of payment with bank statemen...

I've sent them proof of payment with bank statements since the beginning. I went into the dentist only to find my plan had been cancelled in April. No letter, no email, nothing informing me and still was taking my monthly payment. I had to pay full price out of pocket at dentist office. The website also still showed me as be "active." Now they refuse to give me my money back even with proof. Also, I was given a lower price through Marketplace, they had been charging me a much higher price each month. I also sent them proof of that, still no refunds.