When upgrading from a trial, the upgrade will be applied to your calendar immediately. You will be charged automatically for the selected plan when the trial ends.
When upgrading from the Basic (free) plan, you will be charged and the upgrade will be applied to your calendar immediately.
When upgrading from a paid plan, a pop-up will show a preview of the price difference for the upgrade. Confirm the upgrade. Once confirmed, you will be charged for the difference in price. the upgrade will be applied to your calendar immediately.