Write them a stern letter telling them to stop harassing you, especially since you are current. Certified mail. Make sure you send it to the correct address since some lenders have 40 different addresses. If they continue to harass, look for an attorney who specializes in Fair Debt Collection Practices Act, Fair Consumer Credit Report Act and other related laws. Write a letter to the U.S. Office of the Comptroller explaining the situation, and an identical one to the Florida Attorney General's Office.
Why should they leave nasty messages if you're current? Doesn't make sense.