Just use Privacy's virtual cards to sign up for services. If a service doesn't let you cancel, just cancel the card itself. That's what I've been doing.

Of course, it's a different story if you signed some kind of contract, but for the pay-montly kind of things, it's a no brainer. You also keep your real cards number private in case the service gets hacked and Privacy doesn't seem to check the name, so you can give a fake name to the service.