The county probably ran an audit. I get ridiculous notices like that from past hospital vists over things I have already resolved, yet, some person somewhere finds a dime or two and then decides that the arrangements I made previously, sometimes years earlier, are not valid and I need to pay. When I get those types of letters, I call the hospital back and let them know if I EVER get another letter about a bill that has been previously settled, I’ll report them to the BBB and the Florida ethics department. That usually does the trick. I keep copies of all that stuff so that I can prove what I paid and what was agreed upon.