Check in disaster and flight delays

I booked a flight to Durban from Johannesburg from Mango Airlines. The flight was scheduled to take off on the 09th of January 2018 at 08:40am. I got to the airport (OR Tambo) just before 08:00am and I remember saying to myself that I am right on time. When I got to the check in kiosk, they refused to check me in and I was told that I was late for my flight as such I should speak to the guys at the ticket sales kiosk so I can be booked on another flight. The lady at the counter told me that I unfortunately have to forfeit my ticket because I was late and I had to pay for another ticket for which the flight was to leave at 11:40 (this flight was scheduled to leave at 9:40 but was delayed). She went further to explain that I can pay for a seat on that flight but if the flight is delayed fjurther then she will be unable to refund my ticket. She explained that there is a 50/50 chance that the plane will be delayed in which case I will then forfeit the 2nd ticket of the day, I then refused to buy another ticket from them and went to another airline. At 9:41am I was then sent a text message by Mango apologizing for the delay in my flight that was meant to leave at 8:40am and now was leaving at 10:00am and check-in was closing at 9:20 yet they had refused to check me in at 08:00 the same morning. This came across to me as being very *********. The staff were completely clueless and I am really displeased with the airline. In my opinion by far the worst airline I have used and I do not think after today I will continue to use this airline. This is unacceptable!