Independent Advisor for Vanguard Funds Investorplace Media, LLC Won't provide refund as promised Baltimore Maryland

Dan Wiener provides an investment newsletter called The Independent Advisor for Vanguard Funds. I have been a subscriber for a number of years and have nearly a year left on my subscription. He has promised to provide a refund on the remaining subscription if the customer is dissatisfied. 

A portion of the service is called "The Forum", where members may email with each other and further discuss investing and economics. The newsletter made a decision to eliminate this portion of the service, and I made it known that I would like a refund on the remaining portion of my subscription. Dan Wiener/Investorplace/Dan Wiener are refusing to do this because there records do not go back to the time when I paid for my subscription. My understanding of this is that if they do not know what I paid, they do not know what refund to offer.