This is  "collection" agency of some sort.  However said they do not say who "they" are, "what" they are or "where" they are located.  This is a typical please get in touch with us or your representative and if you don't they will "refer" your file for further action.  Now if you believe them and do return their call you are a fool and let me sell you a bridge in Brooklyn.  This is a illegal collection agency or better yet a scam in order to get you scared enough to "pay off" a debt you really don't have, owe or otherwise.