You can remove features at any time. You are only billed additionally for features when you are on the 'Pay as You Go' plan or for features over and above those features included in the Per-User pricing.
Billing for features will stop when you delete the feature. Be sure to confirm that billing for the feature you deleted is stopped by navigating to the "Account" tab and clicking on "Configure plan". Confirm that the 'used' column next to the feature you deleted reflects the correct count.