How do I permanently set up Facebook Messenger as default messaging app?

I go to settings and set Messenger as my default SMS app. The issue is it changes on its own. I find out weeks after fixing it that people have been trying to text me and none of the texts are coming through. I have a Galaxy Crown J7. I can't figure out when the system is changing my defaults on me. I can't uninstall the built in messenges app. I've tried disabling it. Still happens.

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Welcome to Android Central! Are you ever selecting the Reset All App Preferences option in the system settings?

Also, does this seem to happen only after FB Messenger gets updated in the Play Store?

Facebook Messenger isn't SMS, as far as I know - you can exchange texts with other Facebook Messenger app users, but if people send you SMS texts, Facebook Messenger won't get them. That's one of the reasons it switches back - it doesn't "present" as an SMS app.

Can't you still set FB Messenger as your default SMS app, though?