I get these 121-010-0007 calls all the time as well.  I have researched and I am part of an "Alert" messaging for my county and city so I get these when they deem it is necessary to notify us about something like; weather conditions, roadway incidents and other type emergencies.  I think it is a standard text number that comes through AT&T or possibly another carrier.

    Relentless txt messaging . Two to three times a day , even back to back . It has
interfered with the people I care about , since theres no way to screen caller on this cell-ph .
   Secondly , I see it being pointless to do a  report , when nothing will become of it . I would
have no problem going on a hunt , and going postal on this person . Im as madd as hell ,

Who is this odd number coming from?

We are getting this number on our on one of our company phones...Can you please tell me where this number is coming from.  We are also getting this number 121-010-0016, 121-010-0017

texts to cell phone, harrassing in nature, Seth, what state are you in?  I'm in VA