What is the name of your state (only U.S. law)? MI
What does it mean when you receive a certified letter? I definitely owe money and I am concerned it may be a debt collector with something like a wage garnishment?!?!?
A debt collector garnishing your wages would not send you a CRR letter.
DC ~ Can you see it now "Dear debtor: Please be aware that we plan on garnishing your next week's paycheck. This is just a courtsey notice."
When you get a certified letter it means they want to communicate with you. You are better off speaking to them. Putting your head in the sand and making yourself unavailable will only make things harder and costlier on you in the end.
Sign for the letter and then call whomever sent it.