If your loan is an FHA loan, there may be a prepayment penalty that is different from other prepayment penalties. If you do not give the lender 30 days notice of your payoff the lender may charge interest from the date of payoff through the end of the month. This is considered a prepayment penalty and is totally different from the "regular" definition of a prepayment penalty.
I am not sure I would go so far as legal counsel, however, I would first ask the lender (not necessarily the servicer) about the differences in the Note and the original ARM disclosure. Someone more than likely either grabbed the wrong Note or the wrong product disclosure. If this is the case, it is easily worked out. You need to know exactly what the prepayment penalty is all about. If you are not happy with your answers, then contact an attorney.
What kind of loan did you obtain?
When you lose, don't lose the lesson.