Worst service i got from Mat & May

Bought a wallet at Mat & May on the 18th September 2015. Took it back on the 21st September. Wasn't the right wallet i wanted. I've got the original slip and the wallet was and still is in the same condition as what i bought it. So the lady tells me that they cant give me my money back cause they don't have any cash in their store or at any of the TFG because everybody pays with a card. Its ridiculous and they cant even reverse the transaction on my card because it is a mastercard. I need my money and they said i can come back they'll borrow me R100 in the mean time. This is unacceptable . I hope i can get a solution to my problem cause it has been three days now and it's really annoying .