Although we don't have all of the facts here, it sounds like the collector may be violating several provisions of the FDCPA. Find an attorney that handles those matters and fight back.
This is general advice based on limited interaction in an online forum. The reply does NOT create an attorney-client relationship. You are strongly advised to seek the advice of an attorney in your jurisdiction after you have presented them with all of the facts.
If this person was a debt collector then you probably have a pretty solid case under the Fair Debt Collection Practice Act. Debt collectors are required to identify themselves and notify you that they are debt collectors attempting to collect a debt.
While a FDCPA lawsuit may get you a little money and get the debt collectors off your back for a while, it will not address the underlying debt. $17k is a lot of money and it would be worth consulting a bankruptcy attorney especially if you have other debts. So long as you did not sign any promissory notes for the past due tuition it not likely a student loan and would be dischargeable in bankruptcy.
The information provided here is intended to help you be an informed legal consumer and is not a substitute for representation by an attorney.
You very possibly have an actionable claim under Florida's Consumer Collections Practices Act. I highly suggest contacting an attorney to assist you with your case. I personally have experience handling numerous different violations of the FCCPA. Please contact me directly if you'd like to discuss pursuing a claim against this business for these unsavory and illegal actions.
This answer is intended to be used for general purposes only; it does not create an attorney-client relationship.