Disgusting service!!!!!

Pre-purchased extra baggage online on the 13th March(successful) and an additional 5kg on the 14th March prior to wife’s departure to NZ . Upon payment R2800 the qantas website confirmed payment has been received an that extra baggage has been purchased on the 15th. At checkin, my wife was informed that they do not have any record of sort. Confirmed with my bank and the payment was pending supplier i.e Qantas to process. My wife was informed at checkin that quote “it is not their (Qantas) problem” and that she has to pay an additional R4500(airport charge) for the additional baggage and could claim the R2800 once Qantas decides to process the payment. I am absolutely disgusted and will not travel Qantas again!! This is damn ********!