Pay again or you dont fly!even after confirmation!

I am helping my mom sort out a query that we have lodged.<br> <br> We booked a flight from Durban to PE, one way. received the confirmation and code, all was fine. We arrived at the airport, and we were told no flight had been booked and we were to pay R3500 over and above the R1500 already paid for the flight?? how is this possible to give a client an ultimatum and tell them if they don't pay they don't fly and that is that?? shocking attitude. since then, we have had people pass the buck every dam day. YOU should be phoning us to correct what has gone on, it is your reputation on the line yet again. But you instead order us around and tell us to call random people and NO one seems to know how this happened. Your own call center doesn't know?? This needs to be sorted out and needs to be rectified, we have the original confirmation and the newly bought ticket. We need to be compensated for this asap!!