You can remove the screen on your account which will immediately stop any further charges.
We recently released a 'pause' feature so if you go to https://signage.screen.cloud/screens/ and click 'Screen Settings', you will see an option to pause your screen in the sidebar. You can use it to pause billing.
This allows you to log in and continue using ScreenCloud anytime. All the content, playlists etc will still as they are. If you need the service in the future, you can simply go to https://signage.screen.cloud/screens/ and click "Resume Screen".