Technically, if this agreement was never reduced to writing it was never enforceable because contracts that take longer than a year to perform are subject to the Statute of Frauds--Meaning that the contract must be in writing. Assuming that this contract is enforceable, you would most likely be responsible for the high interest, because while it wasn't part of the oral agreement, you mutually agreed to pay the 9.5% when you made the interest payment. I suppose that technically, you could just stop making payments altogether given that it was never really enforceable. Like always though, seek counsel from an experienced attorney in your area that can take all factors into account. Good luck.
My answers to questions are for general purposes only and do not constitute legal advice or establish any attorney-client relationship.
I agree with Atty. Gaskins. The interest charge is likely unenforceable under the Statute of Frauds, whether WV or FL law applies, so the burden is on him. However, if somehow made enforceable, I think you would be subject to the higher rate because you agreed or acquiesced with it by paying it. I don't believe the usury laws prohibit exceeding that rate by two parties willing, informed, in equal bargaining position, and not under duress.
To questioners from West Virginia & New York: Although I am licensed to practice in your state (in WV, on inactive status as of 9/13), I practice on a day-to-day basis in Massachusetts. I answer questions in your state in areas of the law in which I practice, and in which I feel comfortable trying to offer you assistance based on my knowledge of specific statutes in your state and/or general principles applicable in all states. It is always best, however, to work with attorneys and court personnel in your own area to deal with specific problems and factual situations.