@franckowitz,
1. You can always get a bunch of your friends together with signs and do pop-up pickets at the place (spontaneously throughout the oncoming days).
2. You can put an ad in the paper and advertise what's happening with that dealership.
3. You can go in an and rescind the deal (maybe).
4. You can spray-paint their shop saying they're liars, cheats and thieves.
5. It's "faze" not "phase".
6. Contact your bank and see what you can do.
7. Contact your local paper and/or radio and see if they'll do a "Go Public" kind of thing.
8. You can toilet-paper their establishment.
9. Offer free pizza to anyone who's willing to stand out front and chant "This place sucks" for an hour.
10. Hire a band or parade group to troop around and blast them with noise and chaos until they see reason.
11. I have a lot more ideas.
I know you're sincerely frustrated, but c'mon, let's get creative since what you've been doing hasn't worked. Look over your contract. Get tough.