Deposit paid to Right Cars

My partner saw a vehicle and a deposit amount of R5000.00 and 2 days later he went back to them to cancel the deal and ask for the deposit to be refunded to him. The refused to pay him the full amount saying he signed on the dotted lines that should he cancels the deal he will forfeit the full deposit amount. The sales person that was assisting him did not explain that should you cancel the deal to buy the vehicle he will not be getting the deposit back. Right Cars sales person did not provide him with a copy of the contract that says he forfeits the deposit should he cancels the deal.