Changed my flight without notice

I booked and paid to fly from OR Tambo to King Shaka Int. departing at 19:15.<br> <br> 2 days prior to the flight, it was changed to depart at 20:00.<br> <br> This is not what I booked and paid for.<br> <br> I was not explicitly notified about this change, and only picked it up by chance as I had spoken to a colleague who had booked for the same flight.<br> <br> How can Mango just willy nilly change times without even notifying customers.<br> <br> I paid to be in Durban by 8.30pm and will now only be landing at 21:10.