Cancelling your subscription means that when your current licence expires (1 year from purchase), you will no longer receive automatic updates and priority support.
If you still wish to cancel your recurring yearly subscription, you can do so by following these steps. I will use WooThumbs as an example, but all plugins use the same method (just the settings page is different).
Navigate to your WordPress admin area.
Go to the plugin settings page. In this example: WooCommerce > WooThumbs.
Click Manage Licence & Billing.
Click Cancel Subscription.
Your cancellation will be confirmed and you will be notified of your expiration date. The plugin will still work as normal after that date and you may be prompted to upgrade your licence at the time of renewal.