Zety Charged Me Monthly After a One-Time Purchase

I made what I believed to be a one-time purchase on Zety, but I later realized that I have been charged every month for the last four months, even though I have not used the service during this period. I only noticed these recurring charges very recently when I checked my account. The amount charged has been about 24 dollars per month, and the payments have continued without my awareness or consent to an ongoing subscription. My Zety account and payment are linked to the email address sarah10***@gmail.com. Since I clearly did not use the service for these four months and was under the impression that I was making a one-time purchase, I find these recurring charges unfair. I kindly request a full refund for the last four months of charges and the cancellation of any active subscription associated with my account.