Don't buy the flexible ticket from this company

I bought two tickets from Johannesburg to Kasane in Botswana with the flexible option. The tickets were for myself and my mother. I returned on the scheduled date but my mother wished to stay longer. As I was in the middle of the African bush, I could not phone so I emailed GoToGate requesting them to reschedule my mother's flight. All I received was an automated reply stating they would revert to me the following day. As this was too late, we lost the booking and will have to reschedule and repay for my mother's ticket. When I got home from Botswana yesterday, I received another automated message saying that due to the high volumes, they would only revert today. What a joke!