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.
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.