https://thejournal.com/articles/2012/09/18/celly-launches-group-texting-service-android-app.aspx
Celly Launches Group Texting Service, Android App -- THE Journal
Celly has unveiled its free group texting service, which allows schools and universities to create "cells," or private virtual groups, for class discussions,...
group textingandroid appcellylaunchesservice
https://www.textline.com/features/group-messaging
Group Texting for Business: Efficient Coordination
Textline's group texting service allows businesses to communicate with multiple people or groups at once with minimal time and effort.
texting for businessgroupefficientcoordination