Bad Service

On the 2nd of October 2020 I had placed an online order for items that had been on promotion ,I had purchased a few items at 2 for R14 as well as 5 for R10 ,I had also choosen a few other items which were also apart of their 70% off online sale,on the 19th of October 2020 I received an email to say that my order had been cancelled and that I would be refunded in full,unaware of why my order was cancelled or what happened I emailed their customer service and a agent had rep**** to me saying that their was a glitch on the system and it processed the incorrect pricing on the system,they had apologized and given me a 25 % discount. As a customer the price I see is the price I get if there was an issue on their side it's not the fault of the customer.This is really bad service from such a big company given the fact that the brand should value customers .This is a system error so why does it come at a cost to the customer?