Damelin (DCC) refusing to refund what is due to me

In January 2015, when paying at the Durban office, my credit card was swiped twice AND I was charged the wrong amount. I have been trying to get my money back ever since with no success. I even waited for their 90 day waiting period before I started making enquiries. From March 2015 I have sent numerous e-mails and made several calls. I have to send the same information all the time to each new person I correspond with, but no-one wants to take ownership to process the refund. This is thievery as Damelin took money that was not due to them. The right thing to do is to pay back the money!!!!