Did you subscribe to an app through your iPhone or iPad? Maybe it was a free trial subscription that will be charged a monthly fee. It can be Apple's own service, such as Apple Music or Apple Arcade, or a third-party app, such as a password manager and a music streaming service.
If you use the service on your Apple device, you can unsubscribe from it. That sounds comfortable, but how does it work? To cancel a subscription from your iPhone, iPad or computer.