bad faith in the sale of a Merc

Avis Randburg had agreed to sell a Merc C200 at a price of 312000 however when I requested an invoice I was told stories about it been damaged later the same car was re advertised at a different price. I would like to know why this is the case. I lost four weeks negotiating with Avis and I'm told the same car is not available at the same time they advertised the car