Calls everyday but never leaves message

I got several calls from this number. I never answered. Today, they left a threatening email that I had complaints filed against me and if I didn't call them back by tonight, further action would have to be done. I immediately know this is some kind of scam. I'm not about to call them back.

These guys left a threatening message on my answering machine today.  I have a sneaking suspicion this is a scam.

this number has called me twice in the last two days. i answered both. they were looking for some guy, no idea for what, i told them they had the wrong number and told them to take my number off of their list. if memory serves i believe these same people called me about the same person about 1-2 years ago.

This is a company that is threatning and aggressive in collecting info. will not leave message but rather call repeadily.