Welcome to Android Central! What's your question? The Tab E is a tablet, not a phone. Are you asking how to power off your Tab E, or are you asking why there is a Phone app on your Tab E?
I have a similar issue on my samsung tablet e...I have a cell phone so I don't need the app and it is using a whack of ram and won't let me manually disable the way other apps will the usual way...the option is greyed out...any Ideas?