There is a Cordova plugin which allows to send SMS:
github.com/cordova-sms/cordova-sms-plugin
You have two options:
1. Export your game as Cordova project, manually add plugin to the config files. Also add JavaScript method calls like sms.send(...) to your events. You will have to build the Android app using Android Studio or Cordova CLI.
2. Find someone who could convert this Cordova plugin to C3 addon.