I need to stop and Icloud monthly fee. Please assist

See the following from Downgrade or cancel your iCloud+ plan - Apple Support

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.

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