dealership trouble

What is the name of your state (only U.S. law)? new jersey i bought a car and the deal was 5000 for my old car we told them that the titled was being mailed to us and didnt have it yet. the told us to come in the next day and oick up the new car and then charged us 4500 cause we did not have the title for the old car and kept my old car what could i do?

Duplicate thread - see other thread in this forum.