Unilateral change on agreement

On 1st August 2017 I booked a flight from Johannesburg OR Tambo to Cape Town for me, my wife and son. The flight was at 14:35 arriving at 16:45 (JE147) Yesterday i receive an sms notifying me of the flight change now at 15:40. I have already made appointments in Cape Town. This morning i went onto the website i saw the flight for 14:35 advertised. I called the client center and was told the flight is no longer available and we must go to airport and see if we can get an earlier flight. I was also asked to call ********** 002, which i have been told the flight had to go for maintenance and was transferred to another line, put on hold and cut off. I feel this is really a huge inconvenience on my side, a lot of incompetence on Mango and unprofessional-ism on the staff who are there to respond to use as "GUESTS".

I need proper response from management and some compensation for my inconvenience because surely this is unacceptable. Im a Professor at Wits and do not have time to spare at the airport while waiting to be put on a available flight when i have booked 15 days in advance for the trip.