Refuse the gave us the Registration Certificate

On 23/10/15 we went to Longtom Nissan Lydenburg and ask the sales manager l we want to trade our Chevrolet Trailblazer and a Honda Prelude with an ex amount of money if it is nessessary.I told them that I want to leave the Premises with a vehicle and without an car installment.He did all the paper work and inform us that we can take the Tata Xenon. They will settle the Chevrolet take the Honda and R28 000.00 for the Tata Xenon.The deal was done and signed with a cash tax invoice for the Tata.On the 30/10/15 after one week the sales manager called us and said he made an BIG mistake with the deal and that we still have to pay R139900.00 for the tata before we can get the papers of the Tata.Or they want to cancel the deal. The week before we sold the Tata to someone because we know it is ours. We still have to gave them the vehicle documents. They email Wesbank and told them they want a refund on the money they paid for the Chevrolet and I email the bank that they will be liable for the money if they refund Longtom Nissan because we don't have the vehicle, it is in the property of Longtom Nissan.