Refusing to refund R25 000

My father bought a vehicle, he gave a deposit of R25 000 prior seeing the vehicle because that's their policy apparently.when he went to collect the taxi in Vereeniging he was given a contract that had new terms he wasn't told about (this is an elderly that didn't go to school ) and only he had signed the contract. We find out that the car is actually a rental with ANOTHER company. When I called the owner and ask about the signature, hesaid it must've been a mistake from his staff member. We were stuck with a taxi that couldn't be used for the purpose it was intended to because he wasn't given the facts about the transaction. After communicating with the owner, we agree to return the taxi and he will give us a full refund on the deposit fee. It has been two months and still NO REFUND,we have been getting the run around.They have caused a big inconvenience in our lives...