this number called me 3 times but i did not answer

I got an unidentified message from this number, instructing me to call regarding my "private information."  I called the 866 number from an unidentified phone, and I had to ask twice to find out the name of the company, which they only said was "C.A.C.I."  I tried to get more information about what is CACI and what does it do, and they would not tell me, only saying that it was regarding my "private information," and they would not talk to me about details unless I gave them my name.  So, I said, "well then I'm not interested in talking to you."  

Sounded like a scam to me.  I googled "CACI" and nothing came up that looks like a company that would make secretive calls to people.  

I figured if they were legit, they would properly identify themselves... for example, "Consumer Aggravation Company, Inc., based in St. Louis, we are a company that does _______."  Since they didn't, I imagine there is a reason they are hiding, which is because NOBODY WANTS TO TALK TO THEM.

I Got Two Calls From This Number Today. When I Answer They Hang Up.

I also got two calls from this number and when I answer they don't say a word. I called the number back and the recording says it's CACI.  Don't have a clues as to who this company is.

this # calls me quite a bit, although not every single day.  i always miss the call and they never leave a voicemail.  must not be too important.  i tried calling it back once and just got dead air.