Card ***** department won't reverse transaction

My garage card was skimmed on the N3 toll route (go N3TC and your employment of *********) and the ********* racked up R20 000 worth of purchases (i wasn't aware you could buy goods with a garage card - I thought it was for petrol and toll fees). As soon as I saw the transactions, I contacted the ***** department to cancel the transactions and the card. I asked them to reverse these transactions as they were only a few hours old, but they informed me that this would not be done. They would first investigate and if they found the transactions **********, then they would refund the amounts within 6 days. I find this unacceptable that I will now be R20 000 in the hole when I have raised the objection immediately and confirmed that these are not my transactions.