Poor service from Flysafair and airport company south africa

I was not allowed onto my flight to Cape Town FA464 at 16:45 on Wednesday 2nd April. Even though I arrived at the airport well before time, security lines at King Shaka International were out of control and extremely long, which delayed me in the line. Usually, there is some staff member who will call for passengers who are still in the line when the flight has begun boarding. This time, there was no sign of any staff members and the airport was extremely full. Upon scanning my boarding pass, I realised that there is only 3 minutes till the gate closes, I asked the attendant will the flight wait since this queue is so long, to which she rep**** "they wait for noone". I ran to the gate and the staff refused to let me and 4 other passengers who were also delayed by security onto the flight. Even though the flight was still there, and I could still see people getting on to the aircraft, they refused to allow me on. Additionally, my sister was travelling with me and she was just 2 people ahead of me, yet they let her on to the plan and refused to let me on. They then diverted me back to the ticket office to see what the next available options are. Upon further questioning and investigating, it turns out that flysafair had been over booking flights and the manager said they had been having problems for the past few days. Despite knowing they had been having the same problems, there was no effort made to accommodate for passengers, and we were told that we can take it up with Airport companies south africa, as they cannot control security. My question raised was why was there no communication between the security checkpoint and the flights as there were other passengers delayed as well. There seemed to be a lot of shift in blame and no responsibility taken and nor any accommodation for the passengers. Pathetic services from all ends, and all we were given was an email address for us to log a complaint. Further more, i am a student and at the end of the day passengers have to incur extra costs for security and staff issues which are totally out of control and are expected to go through a long process of investigation just to get some form of reimbur*****t.