I want to cancel my membership

Experiences like f4ucorsair's are why I raise my eyebrow when a company requests credit card information for a free trial.  There was no need for any of this hassle & threatening to sue nonsense.

Just sayin'.

Okay.

But auto-renewal is commonplace on all sites run similarly to chess.com so no fault of theirs.

(read the small-print always when subscribing to something:)

How do I know when the ticket has a response?

You'll get an email.  To respond to the ticket just reply to that email as you would any other :)

There's a big difference between "We'll charge you and continue to charge you regularly until you actively stop us" and "We'll let you try out the service for free, but unless you actively stop us we are going to start charging you"

The latter is collecting personal information that is not strictly necessary to render a service (in this case, the free trial)

The free-trial is free?

The subscription afterwards is not. Auto-renewal is commonplace amongst numerous companies as I indicated. (car/home insurance one example)

Only people that seem bamboozled by that are those that have never paid for anything in their lives before.

Requesting credit card info is a perfectly reasonable way to ensure people don't simply float repeated free-trial after free-trial.

Whenever you hand info like that over, even for a free trial, it's pretty important to understand the terms of the agreement you're making -- in this case, the onus to opt-out being on you.

Incidentally, in every case like the I've ever seen here, chess.com has been more than accommodating.

Yeah.

Think they are very fair over money-back/satisfaction guarantees?

If you don't think the site is worth the money do that and leave happily.