Assuming you are talking about receiving email updates, an admin would have to perform a quick SQL update. Again, assuming you have a bunch of subscriptions... This is the easy way to change in bulk.. Otherwise, you can change it yourself through Control Panel>List Subscriptions. Check mark on the right what you want to unsubscribe to, then scroll to the bottom and click the drop down and select 'no email notification'.
SET emailupdate = '0'
WHERE userid = '151318';