the best thing you can do is file a police report on the number

Call blocker might be of some help.  Also don't pick up on numbers you do not recognize, or where there are caller IDs that seem odd.  Or where there is no caller ID.

This number is repeatedly calling my phone and leaving threatening messages about court and "you have been notified". I want it stopped. You can send whatever documentation you have by mail because I don't know just send money over the phone because you TELL me I owe something. THIS is harrassment. They constantly call my phone and as I travel for my job it is unprofessional. I have blocked their number but then they harrass my family. My in-laws are reaching out to an attorney to stop the harrassment

Yes, Same with me. I called and some the person that I spoke to sounded like he was part of a prison release program.  He asked for the last 4 digits of my SS number and when I refused, he said that we will see you in court. He couldn't even tell me what the call was for.  What a low level scam plan.  Even their company is a generically called "National Information Services."  I looked it up and it doesn't even show up on Google.  All the numbers related to this are VoIP which means they are not even legit, permanent phone numbers. They are numbers that are created by services like Skype so they can easily get a number created with the same area code as you. This makes them look like they are "local" to your area but are most likely working out of a bodega in the dark corners of Camden, NJ or something. Report, report, report.

When I called them up and spoke with them a second time. I pretended that I was really concerned and gave them a fake SS number so I could get them to stay on the phone for a while. When they asked me how I would like to pay, I responded by telling them that I had only kept them on the phone long enough for the authorities to gather as much information as they could, including their voices. I have never heard someone hang up so fast in my life.  Haven't had a call since.

Now that's really funny!  Thanks for the heads up...I think that what I'll do from here on out.  When you gave a false SS# they didn't realize it?