unfortunately you are wrong.
No. I may be wrong, or you may be wrong -- as you say, it depends
on the details.
However, the bottom line is that the dealer got a check for 100% of
the car + extended warranty + tax&tags + everything else before
the car was driven off the lot. That's a check (or checks) for the full
amount, up front
. Shortly thereafter, SoA and the "floor plan" bank
got their cut from the dealer. Up front.
With the huge cash down payment from the OP, they could easily
refund the full warranty price, in cash -- because the car is worth
far more than the principal, and the loan will never be upside down.
As someone else suggested, if the dealer and/or bank won't go for
that, I'd be calling my several credit unions with the intention of
refinancing the loan at a lower monthly payment. With any luck,
the original lender would then "claw back" any finders fee paid to
that scummy dealer.
Deducting the refund from the loan balance IS NOT the same as
a "full refund within 90 days."