Big Commerce BigCommerce Offered Free Trial in writing but won't Refund Money , Internet

We checked out Big Commerce for our internet business and were offered a 15 day free trial in writing to assess the product. they required a credit card on file but said we could cancel w/in 15 days so we proceded. We cancelled well within the 15 days in writing but they refuse to honor their offer and refund our money. Customer service is abviously coached to give customers the run-around and theough we have provided all they require we are caught in a terminal loop. I have never filed a report like this for any service before. I employ hundreds of people and know that this kind of "policy" and honest failure is not the fault of the customer service representative, rather it is company policy. I suggest that anyone who values ethics from a vendor partner avoid this company.