But then that becomes unpaid bills and they send you to collections.
When they buy a debt, they rarely get comprehensive documentation.
It's far from a good solution, but it should at least put you in a better position vis-a-vis the courts if it comes to that.
Furthermore, there's an entire category of people for whom "talk on the phone" is not an option, period. If they wanted to cancel by the approved method, they'd not only need to take that time themselves, they'd need someone else willing to take that time with them.