I'm not sure about the specifics, but in the EU it's not legal to offer a sign-up method that is not available as cancellation method.

Do you have a source for that? The Economist certainly doesn't, cancellation online is not possible but sign-up is.

The email method didn't work for me last time, I just got a reply asking me to call them.

Hm, I could have sworn I read about it a few years back that it was introduced. Also, it might have been only Germany? Can't find anything as google has the worst result for that search I've ever seen.