Dealer sells same car to two people

We bought a 2017, I10 from Hyundai Roodepoort from Tinyiko Mthembu. He kindly brought the vehicle to Pretoria for me to test drive, and we settled on a price after he phoned his office and received permission for the discount. I indicated that we will take the vehicle. Back at the office he send a Offer to Purchase that we accepted and made the EFT payment as per OTP. A day later he phoned and said they made a mistake and that the discount of R4369 cannot be granted, but that he has a similar vehicle although not the same colour that we can get for the same price. We preferred the original vehicle as per OTP and informed him accordingly. I then send emails to arrange for the delivery of the vehicle at Hyundai PTA as we initially arranged. When I phoned the Used car sales manager Robert Nelson, this morning, he informed me that they have sold the vehicle that we have bought and paid for. They have our money and we have no car. At no stage prior to this morning during our telephonic conversation was I informed that the vehicle we bought was sold to someone else - this is really bad service!. We still require a vehicle, but have specific requirements - which the original vehicle comp**** with. I now have to resort to legal action as the vehicle we bought and paid for was sold to someone else - and we sit without a vehicle.