Why was this done?

I bought a perpetual license for draftsight in 2016. At the time I thought it was a deal. On sept. 5th I got an email saying I had paid for a subscription on Aug 25. I have never authorized a subscription to draftsight. I promptly canceled it. however I have still been charged \\\$99.00 for something I do not want. So are you so desperate for sales that you would make a fraudulent charge against my credit card? Or is this just part of the scam? If anyone sees this beware of giving these guys credit card information.