Downgrading takes effect at the end of your current billing cycle, so you get everything you paid for.
How to downgrade
Click your user chip in the top-left
Click Subscription & Billing
Select the plan you want to move to
Confirm the change
What happens after downgrade
You keep your current plan until the end of your billing cycle
At the end of the cycle, your plan changes to the lower tier
Your cap adjusts to the new tier's limit
What if you're over the new cap?
If you've already accepted more invitations than the new tier's cap allows in the past 12 months, those accepted meetings stay confirmed. But you won't receive new invitations until enough time passes that your rolling count drops below the new cap.