Online purchase money

I made an online purchase, and it took me to their PYU, which I entered my card details and the transaction was noted as successful. The money was taken from my account and after that they canceled the order and said no payment was made. I have shown them that they TOOK money from my account, and nothing has been done from their side. They have ****** me of over R3000 and none of their customer reps are helpful. They even went to clear the transaction on their side knowing full well that on my side they claim it is unpaid. I drove to the HiFi Corp at Cresta Mall, even showed the manager the transaction with their details and he said "This might be a technical error and we cannot blame anyone", but it is their systems that failed. I should not be ****** from and inconvenienced because their system decided to mess up the transaction. It's very convenient that the system was able to take My money but unable to read the transaction. Even as far as to clear the transaction! I am livid and disappointed at their behavior.