called and no answer

Some long distance service guy called from this number and when I jung up, he calls back and threatens to continue to call.

Keeps calling, no message, any clue who this is?

I use Nextiva (InTalk) VOIP service for my office / home.  If I am on another VOIP phone away from my office / home, the CID shows this number.  If I am being called on my cell phone, it shows the correct home number.  Don't know why.