Over charged by a cashier who could not even explain what the extra amount she made me pay was for what

I went to exchange clothing when I go t to the till the female that was assisting me called her senior to enter something on the system the items that I was exchanging where R110 and the items I had were 100 so this cashier did her job on the till and asked me to pay 256 so I did without asking questions as I was in a hurry to go to nytshift so while in a taxi I did calculations and I recognized that I was suppose to add R10 only so when I was off I went to the shop confronted the cashier n she called the same guy who now claims that I should only be refunded 79 we argued did calculations until the shop closed while inside I asked for the manager this guy came telling me the same nonsense of 79 and they were so rude one guy came he said he is from Ackermans Hr and he sees the mistake that was done by the staff at Ackermans palms springs mall that is wen they gave me my full money back without no apology for their fault and for exposing to be in that shop from 2pm to 6pm remember we living under the. COvid pandemic and they cared less about that I'm very disappointed by ackermans staff palm springs.