I responded to a sales offer that was presented to...

I responded to a sales offer that was presented to by mail to trade in my car and get a specific discount. registered online was told to make an offer I offered the exact terms they had on the ad and they flat out refused to honor it. i escalated it to their manager who refused to honor the terms as well. I showed them the offer mailed to me still no. later I called to speak to the general manager was sent to his secretary and then to a floor manager still no one willing to help or even get back to me? Can car dealerships get away with anything they feel like? are they unaccountable? aren't there both federal and state laws about fraud and false advertising? bait and switch is bad enough but to flat out refuse to acknowledge their own advertisement sent thru a federal entity like the usps?