I see a lot people trying root only for this so I decided to post it.
Its very easy just download this app:
https://play.google.com/store/apps/details?id=com.tapbase.LTEswitcher
Open the app and go to set preferred network type
Select lte only
That all
Note that while you are in lte only mode you can't make calls, you can go back to normal mode selecting it in the app or in Settings/Mobile Networks/Network Mode and select LTE/WCDMA/GSM
Sent from my SM-G935F using Tapatalk
Its very easy just download this app:
https://play.google.com/store/apps/details?id=com.tapbase.LTEswitcher
Open the app and go to set preferred network type
Select lte only
That all
Note that while you are in lte only mode you can't make calls, you can go back to normal mode selecting it in the app or in Settings/Mobile Networks/Network Mode and select LTE/WCDMA/GSM
Sent from my SM-G935F using Tapatalk