How do you shut off a batch campaign?

Is this a Smart Campaign with wait steps? In that case you need to use the flow action "remove from flow" to remove the Leads who are already in the Smart Campaign from the flow. You can create a separate Smart Campaign for this: 
- Smart List: Member of Smart Campaign "Campaign X"
- Flow: Remove from Flow, Smart Campaign = "Campaign X"

Best, 
Jep

The problem is likely (not sure from your description) that you still have leads coming out of a wait step and getting the email from the next flow step.  It's tough to stop this.  You can: delete the 'send email' flow step that is still sending the emails, or disapprove the email altogether if it won't impact another campaign, or find all the leads in the wait step and run a remove from flow action on them for that campaign.

Or, of course, none of those and it's a different problem entirely...