Here in Sweden you can cancel a subscription however you wish (as long as it’s within reason). You can send a company snail mail, email, go by their office, phone, text, whatever reasonably reaches them. They’re not allowed to pull the “Oh, buy you have to call [number which leads to an antichurn department]” or “please tell us why” (but of course they’re gonna try anyway. If it’s an online form you usually have a “I don’t want to disclose why”-reason).