I found this page too late! After going through the multi step cancellation process and being told my account was closed, I just noticed (after the 2nd monthly charge hit) that my subscription was never canceled. I wrote customer service explaining the situation and got a form letter back stating there is nothing they can do.
I found this page because I wondered if they did the same to others. Clearly this is not a one-off mistake but rather the shady way ClassPass makes extra money. Now that I know I will dispute directly with credit card and see where that goes. So be warned -- when you try to cancel, make sure you take a picture of the chat window and get anything in writing if you talk to someone. It's a scam.