Cancel any time at Settings → Billing → Cancel. Paid features stay active until the end of the current billing period; sites are never deleted.
Go to Settings → Billing → Cancel Subscription, confirm, and paid features remain active until your current period ends. After that you drop to Free — sites and history stay, but paid capabilities lock.
Settings → Billing → Cancel Subscription.
Annual plans: prorated refund. Monthly: no refund but full access until period end.