Unfortunately companies like Anthropic like to provide web sites that work long enough to obtain your credit card information, then break them in a way that prevents you from unsubscribing.
Or have it so it's trivial to sign up online, but cancelling requires contacting them via phone/post/whatever. 'Funny' how well these systems seem to work when people are giving you money, but how much of an unusable mess they turn into when it's the other way around.
State Farm wanted me to speak to my agent directly (who they had never bothered to change from one down in Texas when I told them I moved to Montana), so I gave them written notice through the contact form on their website and then had to file a chargeback when they charged me again.
Got a check from them in the mail a couple weeks later. (For $13.83, I'm not sure exactly what that's supposed to represent)
Some banks offer virtual cards directly, but there's also Privacy (.com). For masked email I find Firefox Relay works pretty well.
I like Privacy because they let me switch banks easily, as well as place spending limits, pause or close cards, etc., just like Firefox Relay would allow me to switch emails easily.
I believe I use Firefox Relay for everything email-related now (I pay $1/mo for my own subdomain), and also use Privacy for everything money-related (given they accept Privacy cards).
https://emkei.cz is a good "fake mailer" for getting outbound email from a Firefox Relay address, for those companies that want you to send them an email from the address on your account. Basically you send something from the company's email to your relay address, then reply to it and Firefox Relay will send it to the real company's email, but from your relay address.
(You know, this sounds like it could make for a great phishing exploit because Firefox Relay doesn't check or notify you if SPF/DKIM/DMARC fails on an incoming email, and the forward that it does to your personal email will be entirely lacking those indicators. So aside from email content itself looking suspicious, it could be possible to perfectly spoof a real email because the relay step strips all the original authenticating information.)
I’ve been using catchall email for everything for well over 5 years now, and it hasn’t been useful once since. Regular spam filters from my provider and occasionally hitting “Unsubscribe” once seem to do the trick.