By default, deleted messages are "flushed" after 30 days.  To flush deleted messages right away...

1. Log in as primary coordinator
2. In the URL bar of your browser enter http://<YOURTIMEBANKNAME>.timebanks.org//admin/settings/messages
3. In the "Flush deleted messages" section, change "Flush messages after they have been deleted for more days than:" to zero.
4. Click "Save Configuration".
5. Henceforth, those deleted messages will disappear within an hour (when cron runs).