Pro and Max plans are automatically renewed monthly, unless you actively downgrade before the start of the next billing cycle.
You can downgrade to the Free plan anytime via the Settings → Plans and Billing page/ Pricing → Payment page. The downgrade will take effect after the current billing cycle ends.
You can check your billing and plan information anytime on the Settings → Plans and Billing page or the Pricing → Payment page, including your current plan, remaining credits, and billing history.