I wouldn't even bother going back to that dealer. Take a copy of the sales agreement, if you have it, and go to another dealer. It doesn't matter if the dealer wasn't aware of what the sales guy was doing. If the dealer can't keep tabs and controls on their sales staff then you don't want to buy from them.

I used my Visa for the deposit and then charged $20K of the purchase price on delivery, the max allowed by the dealer, so that I could rack up some points. It was the sales rep who suggested it.

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Wake up every day that would be a start.