A reasonable legal requirement should be that customers are able to unsubscribe using the same method used to subscribe and the process should not require more time and effort than the initial subscription.
Reasonable would be lack payment ending the contract. We should be able to simply stop paying them with zero repercussions. Let them deal with the administrative trivia required to cancel a service.
This TBH, I think we're so used to being taken advantage of that we don't realize we should be asking for more. Especially if it's the kind of service which doesn't involve extra preparation costs for the provider.
The problem is that in the US, one cannot easily stop a debit/credit card from being billed for a particular service.
A more general solution is to make the payment infrastructure allow me to ban a particular merchant. You can implement this by reissuing a debit card, but there's no reason not to make it seamless for individual merchants.
This is the case in the Netherlands and a contract cannot revoke this right (Burgerlijk Wetboek 6:236). If you subscribe online, you should be able to unsubscribe online.
Another thing that helps if you don't want to fight someone who violates this and they require you to send a letter, that an e-mail also qualifies as legally binding. So, if they ask a letter to end a subscription, they must also accept an e-mail.
T-Mobile Thuis literally delayed the end of my subscription by two months, and only cancelled it when I called back. There wasn't ever a way to cancel online. In practice they've really been truly garbage, lawful or not.
Ziggo is similar, very shitty customer service, and you have to talk to an aggressive sales person to be allowed to cancel. The moment fiber was delivered to my area I cancelled them and just hung up on the sales guy lying to me about how their speed was higher (it definitely isn't) than fiber.
Ziggo is terrible. I recently overheard one of their salespersons (at MediaMarkt) claiming that Ziggo is also fiber internet (it's cable). Only when the customer pushed him, he admitted that it is not really fiber, but then argued that it doesn't really matter, because 90whatever percent of the route from the data center to home is fiber.
Their 35/50Mbit upload speed says differently. I'm really looking forward to not having to call them again for discounts (since you otherwise pay more than new customers) because I can then actually leave them when the fiber is installed.
Good to know I just have to hang up on the sales guy.
Member lagadu nearby (root post) states it is the case of Portugal.
Edit: according to member t0mas88, it is not just Portugal, or the Netherlands as mentioned nearby: it should be a European directive, not yet implemented by all Members. I guess that this should push heavily on the service providers for general compliance (as opposed to changing the options according to geolocation, as another member here revealed mentioning California).