HAHA... look what i have found in android 6+
when you go to settings, app manager you can turn off "BACKGROUND" mobile data to each app what means your app will not be able to download anything (access any url) when it is in background.
so ads will still work only background activities will be not able to use mobile data (wifi will still work).
i have the filling that soon (maybe android 7) they will also let u choose whether you want to disable also mobile data when the app is in forground.
i guess i will need to look for a new hobby then coding