how to downgrade iCloud storage

If you cannot click on Done, you will have to reach out to Apple Support per -- Downgrade or cancel your iCloud storage plan - Apple Support.

"If you can't select Done

If you can't click Done, make sure you are signed in with the same Apple ID as your iCloud storage plan. You can also try following these steps on a different device. If you still need help, contact Apple Support."

It'll downgrade once you reach the date of your monthly subscription