First, if the bill is 15 years old and no one has paid anything in those 15 years, the debt collector should not be able to place it on your credit report. Generally without a judgment and with no payments, a debt is only allowed to remain on your credit for 7 years.
Second, the statute of limitations, which is the time in which they can enforce the collection of a debt through lawsuit, likely passed after five years of non-payment. This does not mean that the debt collecter can't request that you pay, only that they cannot sue you to collect.
Third, you should consider sending the collecter a written dispute letter and demand that they cease communications with you. If you do decide to send the letter, you should send it either by fax (and retain the confirmation page) or by certified mail. If they continue to contact you after receiving this letter, you should consult with a FL consumer attorney regarding the possible FDCPA violation.
I would definitely seek an FDCPA attorney because they may even pursue this for free if there are attorneys fees in the statute that apply.
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The Fair Debt Collection Practices Act prohibits debt collectors from suing or even threatening to sue you for a time-barred debt, but that doesn't mean a debt collector can not ask for payment. I agree with counsel above and would add only a recommendation you issue a debt validation request, and include a statement that the debt is barred by statute since it is 15 years old.
Please note that this answer does not constitute legal advice, and should not be relied on, as each situation is fact specific, and it is not possible to evaluate a legal problem without a comprehensive consultation and review of all the facts and court pleadings filed in the case. This answer does not create an attorney-client relationship.
The statute of limitations has long passed. However, if the creditor files suit and you don't raise the issue of the claim being outside of the statute of limitations, you can effectively give them a judgement by waiving that defense. I would make sure the $199 is not reported on your credit.