Welcome to the community Amy. First I would suggest contacting the court with that docket number to see if a judgment was filed against you. If so you will need to speak to the judge who oversaw the case and let him/her know that you were not served and that you need to motion for the judgment to be vacated due to improper service.
I would also suggest sending this law firm a debt validation letter (you can find a template via my signature link) send it certified mail, return receipt requested.
So far the violations that I can see (Fair Debt Collection Practices Act) are:
1. Calling you at work when you have notified them that such calls are inconvenient or not allowed.
2. Speaking in a manner in which to abuse or oppress the listener.
3. Failure to send written notification within 5 days of initial contact.
I would suggest filing complaints with your state Attorney General's office as well as the Federal Trade Commission. Additionally you can find information on vacating a judgment via my signature link.