ILLUSTRIOUS PERKS snatched my money without my consent Internet

Illustrious Perks pulled out $48.88 from my checking account without my knowledge. They said that when I was purchasing something online that I had signed up to be a member with their company. So fine, I called and cancelled my membership. They told me that my $48.88 will be refunded between 7-10 business days. Well its been longer than 7-10 business days and no refund yet. So when I called the company to see when the money was going to be posted in my account, it showed on their end that the check cleared and was put back in my account. However, on my end the money was never posted up. So I asked them what to do next, they told me to fax over my bank statements for the month of July to prove to them that I wasn't lying and that my money was never posted. Well according to them, the bank statements we're not good enough for the refund. They wanted a letterhead from the bank stating that the money was never refunded to my account. Unfortunately my bank doesn't provide letters like that. So what I did was, I called Illustrious perks and my bank and had them on 3 way calling. That still wasn't good enough for I.P. So now Illustrious Perks refuses to give me a refund without that letterhead and there nothing that my bank could do anymore. I even tried to file a claim with my bank but they said they couldnt help me with my situation. Illustrious Perks couldn't even provide me with a confirmation number or a copy of the check showing me that the money was put back into my account.... What am I supposed to do now? Am I supposed to be assed out of the 48.88?