Service Plan is worthless and not worth the money.

Two things:
1. Read everything before you sign it. Most people don't read it and sign it as the finance guy explains it but unfortunately many are taken advantage of (like you).
2. You can get a refund, however, it will be applied to the END of the loan (if you got a loan for the RV. If you paid cash it will be pro-rated and given back (when they feel like issuing a check).

Good luck and hopefully you can educate others before they sign.