Cancelles Flight, No Explanation

I booked a flight from Port Elizabeth to Johannesburg on Sunday for Monday's morning flight which was to depart at 09:10 this morning, I checked in online the night before, I was even at the airport in time because I had a 12:00 meeting in Johannesburg. The flight was first delayed to 10:45, then 2 minutes late they cancelled the flight with no explanation, all the passengers were queing for explanation but none was given, I was then put on British Airways which only left PE at 14:00 while my interview was at 12:00, I lost a potential job offer and I still do not know why the flight was cancelled, I am very disappointed with this airline.. Today's service was the worst I have ever received from Mango. It is the last time I will ever take this airline