Need legal advice

Slmz /hi. We bought a car recently. The dealers supposed to give us two months money back because the invoice for the car was made out two months befor we getting the car. We did a trade in. The car we had was in full working cond. Now that the dealers ve the car they ve issues wit it. So they don't want to refund us the two months money cos they havin issues wit our trade in. They say the evaluation is different now cos they ve to fix our trade in car. Please help with advice. Thanks