If I don't have my old phone and the Windows 10 app is borked, how do I cancel?

My boss switched me out of the Apple ecosystem when he decided to buy a Samsung Galaxy S22 for me to replace my broken old iPhone 8. I no longer use any Apple products as a result. I decided to opt to pay the $1 to use iCloud one time to transfer all my stuff off my phone, and now I want to cancel my subscription. When attempting to log in to the iCloud for Windows (10) app, it beachballs for several minutes before erroneously telling me there's some sort of problem or lock on my account (I then successfully logged into my Apple account in a browser window on the same device).

If I don't have access to a Mac/iPhone/iPad and the Windows app is broken, how do I cancel this service? Also, why is this system so unbelievably user-unfriendly and poorly designed that a single app being broken means I can't easily cancel a subscription?