Hi John,
These guides should help you cancel the subscription and prevent further charges:
How to manage my billing information - PC HelpSoft
How can I stop my subscription and cancel automatic renewals? - PC HelpSoft
If you have any additional questions or concerns regarding this, it would be best to contact their support team and perhaps try to request a refund if eligible. You can submit a request (email) or there’s live chat and phone call options here:
https://pcsofthelps.com/contact.aspx
Subscription Management - PC HelpSoft
If there’s still no success with cancelling the subscription the above way, reach out to your bank/card issuer to block the charges for you. This alternative route may be easier anyway.
Also see Dave’s answer in this thread:
PC Help Soft - Microsoft Community
Hope this helps.