Your ESUs charges will stop immediately in the following cases:
You manually cancelled your subscription for any reason.
You migrated your SQL server to Azure; no manual cancellation is needed.
You upgraded your SQL server to a newer version; no manual cancellation is needed.
If you cancel your ESUs or unsubscribe without migrating to Azure or upgrading to a newer version, the billing will stop billing immediately, but you will lose access to the future patches.