They can call your place of employment until you or your employer tells them to cease.  If they don't cease then it becomes illegal.  More than likely they are crooks anyway and will move on once your employer makes it known that they cannot be intimidated or embarrassed into paying the ransom.

They keep calling me at home and now at my workplace. They say that they have legal documents to serve to me, but nothing ever happens. I think this type of call is illegal. If they don't stop I will turn them in.

Yes, they are calling my cell phone claiming to be the clerk's office and if I don't call back within 24 hours I will be served at my employer and home address will have been verified.  Number is blocked but they leave this number, no company name, etc.  I didn't think they are allowed to call your cell phone.  Furthermore I have no debt because I filed bankruptcy!

I have received numerous calls from this number stating that they have important documentation for me and if I do not return their call then they will submit the papers to the clerk's office. Always calling from a blocked number but leave a number to call back with no company name and when called back they are ignorant stating that they got my phone number from a relative. It is hard to get a phone number from a relative when all of my family is deceased.