Store failed to exchange my charger (Cash Crusaders Arcadia)

I purchased a USB charger for my cellphone 7 days ago at a cost of R79:90 at Cash Crusaders Arcadia in Pretoria and yesterday I realized that this USB type C does not transfer data. I then went to the store to exchange for a better charger as one would think of doing so to retrieve the value of their money. The store employee refused to help me with my problem. They said they cannot help me as I needed help and knowing that I have spent my money making this purchase. They only referred me to a 48hr return policy written at the back of the receipt. I am now struggling to do my work because the cable I bought cannot transfer files. The charger I own now is very expensive and useless. I have tried to explain and show them that this was my second purchase from the store but they ignored. I recommend that other customers should buy small items at other shop than this shop.