To cancel a subscription, go to "Account Settings" => "Subscription" and in the bottom click "Cancel subscription to the PRO (or Advanced), plan:
After you click "Cancel subscription" button, you will be redirected to the subscription cancellation page
with the brief explanation of what happens after the cancellation:
click "I still want to downgrade" to cancel the subscription auto-renewal.
Note: after the cancellation of subscription its features will remain available until the end of the paid period (30 days from the payment date)