Some apps depend upon background data (transferring data when not directly in use). Restricting background data may cause those apps to stop functioning unless a Wi-Fi connection is available.
If using Bixby Voice or Simplified view, you must switch to standard view to navigate the steps below. To modify the view, swipe the Status bar down then navigate: Settings icon > Menuicon > View as standard list.
From a Home screen, swipe up or down from the center of the display to access the apps screen.
These instructions only apply to Standard mode and the default Home screen layout.
Navigate: Settings > Connections > Data usage.
From the Mobile section, tap Mobile data usage.
Select an app (below the usage graph).
Tap Allow background data usage to turn off .
Click here for info on setting data limits and warnings, changing the usage cycle on your device and viewing data usage by app.