Then you need to broaden your definition of texting 🙂 SMS is how texts originated for sure, but today, texting is much more expansive.
There is no need to use FB or anything else for texting. I have an Android and use the default Samsung messaging app to send texts over WiFi when I'm at sea. It's easy and free (other than the cost of the WiFi, of course).
While using FB Messenger or WhatApp is *also* fine, it requires the other user to have that too. With your normal messaging app, the other person just needs to have *any* app that can receive texts. To my knowledge, 100% of smartphones have this.
If you are unsure how to text over wifi, a single Google search will return a plethora of results showing you how.