Over booking the flights to make more money.

My boyfriend and I went to Cape Town International Airport 2 hours prior our flight this morning. We did the online check in on whatsapp and went on to have breakfast. We never received any message saying our flight is being boarded like usual. So we went to the gate in any case on time. Just to find out the gates have already been closed. The arrogant staff members said we “missed” our flight and should go rebook tickets. They wanted to put us on a stand by list for R300 each or R500 each for a definite flight in two days to OR TAMBO. I haven’t seen my family in almost a year and now the tickets are costing me 10k just to be able to see my family for one day.