Use APKPure App
Get SA Group Text plug-in 18 old version APK for Android
Mở rộng giới hạn tin nhắn SMS cho các nhóm Văn bản SA
Due to Android’s SMS limitation, each app can only send 100 messages within an hour. You need to install this plug-in to extend the SMS limitation for SA Group Text.
After download, please go to your app’s settings, then go to app manager, grant Send SMS permission to this app.