Thats not a reliable way to cancel. As long as your bank keeps processing claims against it ( many times thats a good thing for customers) CTCT will keep billing it.
The last thing these folks like to do is to interrupt their cash flow. They're kinda seedy like that.
If you're trying to cancel you better call them.
You ask a great question, and I'd be happy to try and explain what's happening. Many different banks and card issuers will continue to allow charges to process from recognized merchants, even if the expiry has changed, so as to avoid interruption in service. This is in many cases a benefit for people who have recurring bills so that they do not have to go in and individually update card information across a vast array of services. If in your case the charges are unwanted and you'd like to close the account then please give our Billing Department a call at 1-855-229-5506 M-F from 7am-9pm ET. Our billing department will make sure your proprietary information and contacts are removed from the account and can then cancel it so as to avoid any further charges. Thank you!