Toggle 3G (com.ryosoftware.toggle3g) on Google Play
This app includes a simple interface (and a widget) to control the mobile connectivity.For Android versions since Lollipop it only works if the device is rooted.This app is usable for free, but if is the case, it includes a 5 seconds delay before process the requests.Also, it Includes settings to automatically disconnect mobile data when screen becomes off and to reenable when the screen is turned on, and also a convenient shortcut in the statusbar.