This was the solution, thank you! Samsung Keyboard on my S7 cannot be disabled, but when I was in the Text Message app, i pulled down the notification screen, and from there was provided the option to select GBoard. Yayyy!!! Thank you!
Scrowes solution worked for me, on a Samsung S5 with Android 5.0. What a relief!!!
"Found a solution at least for Samsung, go to settings>application manager>all>google app>uninstall updates. after that you have to go to playstore >settings > turn off auto updates."