How do I cancel my iCloud 200 GB storage plan? And, how do I know if my storage is below/above 200 GB? Thank you.

Cancel upgraded iCloud storage by downgrading to the free 5GB plan. See instructions in: https://support.apple.com/en-us/HT207594

To see how much you are using, see information in Manage your iCloud storage - Apple Support

See the following from Downgrade or cancel your iCloud+ 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.

I need to cancel my 200GB data storage plan as I won’t need it anymore. Option to change on my iPhone doesn’t allow me to select 50GB and click ‘done’ Assist urgently?!