Of course it can be cancelled and you should be entitled to the money back. Happened all the time when I was selling cars. We thought that we could get a certain interest rate, but when the bank looked at it, they sometimes had a different view of the situation because it was THEIR money they were lending.
If the RV financing is like auto financing, you will have a shorter term and a higher interest rate the older the vehicle is. Talk to the finance manager and see what the bank's rational is for such a high interest rate before walking away from the deal. The bank just might not have a strong desire to finance a vehicle that old, you might have some issues on your credit report that dictate a higher APR...etc,etc.
You might be able to find a newer model of RV that the bank would give you a better interest rate on and get your payments closer to where you want.
Giving advise without knowing all the facts is a risky at best, but generally speaking from almost 8 years in the car business, try to arrange your own financing ahead of time and see if their banks can match it.
