Complaint - bad Online service

I did an online purchase at Makro in the beginning of April. There was a special on Epol dog food 2x 20kg for R609. I did my purchase checked my order and processed it, but I was charged in full for both bags. Since the day I made the purchase I am struggling to get through to Makro to please refund me the difference. Keeps on getting dame msg. We are extremely busy, we ave a back log, please call later and still nothing. Please refund the diff that is all I ask