Using my calculator, I come up with this:
Monthly Payment = 325.15
Amount Financed : $ 30000
Finance Charge : $ 28523
TOTAL CONTRACT VALUE : $ 58523
Here's one way to think of your Finance Charge Rebate: If you make payments for the full 15 years, you would end up paying $28523 in interest. If you paid it off in one year, you would expect NOT to pay all that interest, right?
Under a Rule of 78ths contract, if you paid off your loan in the 12th month, you would normally receive a rebate equal to 4 years of unearned interest.
If they are telling you that you are not entitled to a rebate of the finance charge, then that means even if you pay the loan off next month, they are going to charge you $28523 in interest. And from what it sounds like, they will charge you a penalty on top of it.
If you know with 100% certainty that you will not ever pay it off early, then you don't need to worry about a rebate. If you do want to pay it off early, though, you will get screwed.