Urgent Documentation need to be delivered but no one answered

Scammer calling from "SG Services".  I wouldn't recommend calling back.

Likely a collection agency, working with very old accounts (at least four years old) which are possibly already closed. They left a recording threatening that if they did not hear back "the information will be issued". I'm not even sure what that means, but it sounds like a boiler-room collection-agency tactic from my side of the call.

I received the same phone call with the same message.  Unfortunately, mine started out from a person saying he was a courier needing to deliver urgent legal documentation, so I called them back.  Now I will probably have an unwanted and unnecessary battle on my hands.

Got the same call yesterday.  After reading the above responses, chose not to call back.  I was told it was urgent legal documentation that required a signature.  If they did not hear from me in 72 hours the "information would be issued".
Thanks to all of you who posted.