Call them. Ask to cancel. If the call takes more than 5 minutes, call your credit card company and issue a chargeback, explaining that you attempted to cancel online, and also attempted to contact them. It costs the vendor money when you do this, and if enough people do it, they lose the ability to accept credit cards.

The process is usually painless, since the card issuer has a financial incentive to screw over the vendor. Some credit card companies will even block charges from a company moving forward.

One of the credit reporting agencies (Experian?) started charging one of my cards without permission. I don’t know how they even got the number, so I did this.

The credit card company operator said a double digit percentage of the call center load was blocking that particular credit agency, and did it with no further questions. I have no idea why they weren’t kicked off the processing network for elevated fraud rates.