You may want to see if your bank will let you create disposable cards. I have two credit cards where I can create temporary or reloadable cards at no charge for transactions.
So if I wanted to trial something, I would create a card with $1 on it. The trial starts and does the test transaction. I forget to cancel before the trial is over, but the card has no money so it automatically cancels.
If I wanted a subscription to HBO, I could create an HBO card and load the amount for it every month. When I cancel, I don’t have to worry that they’ll try to keep charging me because I just don’t add anything else to the card. It also makes me think about whether I’m using a service every month.
It saved me a few hundred bucks not terribly long ago. I tried a clothing subscription box that was absolutely terrible. So I contacted their customer service to cancel because they don’t have a real way to do it on their site. They didn’t get back to me in time and attempted to charge my card for another box. Luckily it was on the temp card and there was no cash on it so I just got a rejected charge on my card.