So here is the scenario, you only have a mobile data in your Android Smartphone but no Wi-Fi that you can connect with because you might be far from one or your nurses are very stingy about sharing the Wi-Fi.
You also have no more SMS/MMS load allocation to send a text message but wanted to reply via text messaging. Now here is a solution unto that scenario. First thing is that we have to also be certain that the recipient of the text message also had enabled this functionality in the "Messages" app otherwise it will not work.
You can go here to read and learn more about it and how can you benefit from this seemingly very useful functionality from Google in the Messages app in your Android device so that if we have a non-expiring data connectivity we no longer have to load our SIM card with extra SMS/MMS allocation.
Your Mobile number must also have to be verified in order to use the function. The workarounds to that is just simple and straightforward. Now after confirming the One-Time Password numbers that is sent to your Phone you are now set to use that functionality for your convenience and interests.