Your paid subscription can be canceled via 'Profile settings' - 'Billing' tab at any time. See the sections below for more information.
Note that once the subscription has been canceled, your account will become free immediately.
Canceling your subscription in Saimaa (2020) interface
Click the cog icon ('Profile settings') in the top right corner then select the 'Billing' tab. Next, click the 'Cancel' link next to the name of your plan, select the reason for canceling your subscription and click the blue 'Cancel subscription button':
Canceling your subscription in Ruovesi (2017) interface
Click your profile picture in the top-right corner, then click 'Account Settings' and select the 'Billing' tab on the left. There, click the grey button that reads ‘Cancel Subscription.’