what do I do if i get a call from an unknown source stating I have a claim against me and will be served at my home or work. Is this a legal process?

I received a call from someone who is saying that I have a claim against me. The call is from a firm called Lombardo Danes and Moff. They are threatening me with court and say that they will be serving me at my home or place of work. They have included a phone number and a claim # , They say this is a civil complaint brought against me. I assumed it is a bill collection tactic...but worried that it is legit. Should I be concerned? I googled the names of the lawyers and cannot find anything about them in a search. I have some very old debts from 15 yrs ago and believe that this might be related to them for a collection. But I don't know how a legal process works as to notify me. I have had no papers delivered to me in the mail from the firm of Lombardo, Danes and Moff. Something doesn't feel right about this call.Please give me your best advice, as to what is legal for them to do and what is best for me to do. At this point, I have not called them back.