Welcome ******* me into signing the contract at home on the evening and not in the garage with him, I was trading in my car BMW due to financial problems

Welcome ******* me into signing the contract at home on the evening and not in the garage with him, I was trading in my car BMW due to financial problems. I wanted a small car and pay R3500 (73 months) or less as I was paying R4300 for the BMW,he said I will pay less for a very old polo vivo that was involved in an accident. He negotiated that I pay R3700 something in 84 months, and hid it from me. I ended up surrendering the car as it was a *******, and had to pay the remaining R75000 to the bank.