SMS gateway on Android?

Question

Android

Hello, I will immediately describe the task - you need to both send and receive SMS on the local network.
At the moment I have a ZTE router, which has a Rest-api web interface, i.e. there, with a simple curl, you can send to a specific ip from my system to the router and receive SMS via JSON or send it in the same way.
But now, for some reason, I want to take any tele2 smartphone for 1700, install an application on it that will be an SMS server, and communicate from my system via Rest-api, sending POST requests to the smartphone and communicating in this way.
And now the question is, is there ready-made, preferably tested and without bookmarks software for working with SMS on your smartphone without third-party servers!
If anyone does not understand, this is part of my system that sends me notifications or receives commands from me via SMS when I am in a village without the Internet.