I canceled the free trial in my head, but the charge says otherwise

I signed up for a seven-day design-app trial to make one graduation invitation. I finished the invitation, downloaded it, and told myself I would cancel the next morning.

The charge on my card says the next morning never happened.

My first reaction was that the company had made cancellation impossible. Then I checked the receipt and found that I had started the trial through my phone's app store, not directly through the design service. I had been searching for a cancel button in the wrong account.

The subscription page showed an active annual plan. The price and renewal date had been visible when I enrolled, but I had treated the trial as a temporary event instead of a subscription with a future decision attached. I also discovered two accounts using different email addresses, which explained why the design website showed no paid plan.

I canceled the renewal through the account that actually controlled it and saved the confirmation. I am separately asking about a refund through the official purchase channel, without assuming that cancellation and refund mean the same thing. The outcome may depend on the terms and timing, so I am keeping the receipt, trial screen, charge date, and support response together.

For future trials, I want a less heroic system: note who bills it, record the renewal price, and set a reminder several days before the decision point. Canceling immediately may be best when access continues through the trial, but I need to verify that rather than assume.

What small habit has actually stopped free trials from turning into surprise renewals for you? And when a charge appears, what evidence helps you find the account that owns it fastest?