Swiss Sciences They originally claimed they received my returned product then when file a dispute with my bank they denied they received and will not issue my a refund. Clearwater, Florida

I purchased an item in Nov. 2010 and thought it was free. When I got billed I called Swiss Sciences and they gave me an  RMA # to return it for a refund. I returned it and on the phone someone named Angel Quinnones said they received the item on 12/23/10. They said I had to go through my bank because I used a debit card to pay for it. I went through the bank and they could not help me. They said the company told them they never received my item. I now call Swiss Sciences to look up my information so I can somehow get a refund and Angel Quinonnes tells me that the computer screen is locked and he can't see any information because I disputed the claim.  How can I prove I returned this? I should have sent it certified mail. Where do I go from here to get a refund? Who can I report them to?