Turning off mobile data for youtubetv

[B1shop]

Quick question. 
Have an issue whereas my YoutubeTV app works great but sometimes my wifi signal will drop. Then YoutubeTV will run on mobile data which I don't want. Can get expensive if not caught. I've turned on Data Saver. Also have gone to the application data usage and turned off allow background data usage and allow data usage while Data Saver is on. 

To test this, I've turned off wifi and still YoutubeTV jumps to mobile data and streams. And it's not cached data that streams for a few minutes before I switch back to wifi to reduce the chances of incurring mobile data fees.  Just to be clear, I understand that I'm dropping wifi. That's a separate issue. I want to ensure that YoutubeTv doesn't use mobile data regardless. Any ideas?

[BandOfBrothers]

Is there any options in the apps preference settings @B1shop  ?

Settings, Apps, Choose App. Tap on Mobile Data, adjust the settings.