If you cancel your service with Clear, I would strongly urge you to report your credit card lost or stolen with the issuing bank prior to canceling service with Clear.
If you cancel your service with Clear, I would strongly urge you to walk into the bank and close any checking account which Clear has record prior to canceling service with Clear.
Cut Clear's purse strings off prior to canceling service, so Clear cannot charge any or your accounts. Be one step ahead of Clear.
If Clear threatens you, I would write a letter of dispute and send it to their corporate office via certified mail with return receipt. Keep copies and records of all the correspondence and postal transactions.
Disclaimer: This information is not to be deemed as legal advice in any manner. Consult your own legal counselor in your area.