Do you have to be notified if you being sued by a creditor or collection agency

Yes, you have to be served with papers (a summons/complaint). HOW you are served varies by State - personal, mail, substitute.

This is your constitutional right of due process. Before legal action can be taken against you, you have to have your day in court. The NY AG recently filed suit to overturn about 100,000 judgements where the plaintiffs used a process server that did not legally serve defendants.