Your phone is capable of handlig two messenging apps. If you are not using Facebook messenger proceed as follows: 1. Do a backup. Go to Settings, scroll to Backups. Back up using BOTH the Samsung and Google backups ensuring messages are included. This is so you don't lose your messages history. 2. If you are not using Google Messages app install it. If you are using it, next step. 3. Go to Settings, scroll to Apps, top right corner, 3 dots, select show system apps. Scroll to Mess... 4. Check or add Google Messages from Play Store as default app. (Settings, search for default app) 5 Test, restart. 6. If still a problem, find Messages app, select Properties, then clear caches (losing settings and history of messages). Restart and test. 7. If you have lost history then go to Backup and Restore, choosing the default message app to restore to. No guarantee of recovering history.
