Mango Airline's Service disappointing.

I had booked for flight to Durban and my departure was 14:55 I had arrived at Or Tambo 14:40 and I was told I was late and they had already closed the gates. They advised me to go to Mango help desk so that they can check for me if there was space available for me on their next flight, then I asked if there were no delay on the flight and I was told no. The lady then advised me that she'll put me on the waiting list for the next flight to Durban and my charge would be R800 and odd rands. I decided to go back home as I couldn't afford paying that amount. And around 16:08 I received an sms saying the Mango team apologises for the delay on my flight to Durban of 1 hour and 1 minute I'm so disappointed and I demand a refund....!!!!! In December also I had booked on line for me and my two girls, booked for seats then when I went to check in the seats I had paid for were given to other people....!!!!