Incorrectly Charged

Hi, I booked a return ticket and needed to change my ticket from tomorrow evening for this evening, 21st.

Called *** after not getting response on charge from email address, lady said there would be R280 charge which included late fee, fine. I paid but when I got reciete via email showed credit for ticket was R350, whereas I had paid R450. Why wasn’t the entire R450 credited since I was charged the R100 to change and R180 admin fee??