I don't know how well it would work in practice, but every time I see something like this, the darker, more childish part of my brain wants me to send a human shit to them in the post, with a note saying "Thank you for subscribing to Post-me-a-poo (Daily)! To cancel your subscription, please add a 'Cancel Subscription' button to your website!".
I have actually threatened this before to some shitty scam company that kept phoning me during work hours - I never went through with it in the end though, because I'm a massive coward and I'm frightened of negative consequences.
But in a parallel universe, I stuck it to them bastards :)
You might be surprised. They still have to pay for office supplies, it contracts, keep the lights on. And I have a have time they are spending top dollar on accounting professionals or software, so they might pay out. It's quite random, and I have often seen the decision to pay a bill based off the size and name of the company lol. Bad spending controls starts with bad companies, and companies willing to go to war pinching pennies from people who barely have it don't exactly make it into my books as a company I bet is run well. You can make a lot of money and accidentally pay a lot of money you're not supposed to. School systems are notorious for being scammed because they have weird, or barely any spend controls.