Mango changes flight time 3 days before flight

3 days before I am scheduled to fly from Johannesburg to Durban I am informed by email (then by SMS a day later) that the times of my flight have changed from +/- 10:00 to +/- 16:00. Without going into the details I could not make that time and had to book another flight to leave out the original time I intended.

Now whilst I imagine the change in time was unavoidable, Mango refuses to provide a refund for that change that they had made. I would not have asked for a refund if I couldn't have made the flight due to reason on my side.

They have promised a credit voucher but I am not holding my breath since they have yet to respond to my email that was supposed to get me this voucher. It is a moot point anyway since I don't intend on using Mango (even with a voucher again).