I cannot cancel my iCloud will not let me downgrade
Why can’t I cancel my iCloud subscription
iPhone 12, iOS 15
Cancel upgraded iCloud storage by downgrading to the free 5GB plan. See instructions in: Downgrade or cancel your iCloud+ plan - Apple Support including the following:
If you can't tap Done, make sure that you're signed in with the same Apple ID that you use for your iCloud+ plan. You can also try following these steps on a different device. If you still need help, contact Apple Support.