I think the common denominator is Group Me. I never had issues until work wanted me to use it and now I get prank calls from many different numbers . Blocked
After I downloaded GroupMe onto my cell phone, it sent a code to this number.
I got a response back that GroupMe then immediately used to authenticate me to the app.
Wish it wasn't so cryptic though. When I first saw this in my SMS history, I got very concerned until I realized the time frame in which it occurred.
This is from the GroupMe app if you text it it will respond with "Sorry! That's not a valid GroupMe command. Text "START" to create a new group or "HELP" to see available commands." Or if you type in what you are prompted it will send other auto-messages.