To unsubscribe a subscriber, read this.
You can track those users by using the Subscriber Lookup Report. You can access this feature from the Events System Maintenance page.
The tool is simple to use. Merely enter the first and/or last name of the patron in question. You can also search by email address. If you check "Show All Names", all subscribed uses will appear.
The resulting list allows you to view or edit the subscriber information, as well as see all the feeds that user is subscribed to.