We do not end listings if you cancel your subscription, they are just no longer kept in sync with your Shopify store and orders are no longer transferred to Shopify.
Merchants can cancel themselves in the app, email support@codisto.com for us to cancel them, or delete/uninstall the app and communication with Shopify and your marketplace(s) will cease.
For further assistance, please reach out to marketplace-connect@shopify.com