Disabling the app is a temporary measure - normally to allow you to fix up some scripts or data without live users using your app (and complicating that work).
We still bill for disabled apps. So, the better way to suspend your app without be charged as following:
Create a new app in brainCloud (to hold the metadata for your Dev+)
Go to your existing app, and push a copy of it to your new app. You do this via the Design | Core App Info | Admin Tools - the Deployment section at the top. You should probably uncheck all of the options so that everything gets copied over.
This will push all settings, cloud code scripts, and custom files to the new app. It does not push player data, or Global Entities. If you need to transfer Global Entities, you could do so via the Export / Import options under Monitoring | Global Monitoring | Global Entities.
Now that you've saved of your work - we'll delete the original app:
Go to Team | Manage | Apps - find your Dev+ app, and choose Disable from the action menu. You need to disable an app before you can delete it in brainCloud.
Then from that same action menu, choose Delete. This will delete your app and all of it's data - and while it's at it, cancel your Dev+ subscription.
You will receive a pro-rated charge at the end of the month.