Who called from 5750000000

Have had several calls today from this number. Caller id shows the number as well. When answered it clicks and disconnects.  when you call it back it doesn't go through. *69 lists the number as 575-000-0000

I received several calls from that number yesterday.  It did not identify the caller, so I did not answer it.

Who are these people?

They want a child support case number

575-000-0000 keeps calling.  The first time I tried to answer it, but there was no response.  This number KEEPS calling.  Wish I could make it stop.  I am no longer answering calls from this number.