Use the following steps to change the Default SMS app to the app of your choice.
Setting the default app
1. Slide the notification panel down from the top of the home screen and tap the Settings icon.
2. Select Apps & Notifications > Advanced.
3. Tap Default apps.
4. Tap SMS app > select the app you would like as your default SMS app.
5. A popup window will appear letting you know to reboot and unlock your device before the changes will take place, select Ok.
Note: The selected app will manage, receive and send all your text messages.