Miscommunication by staff at our expense

Our initial departure time from OR Tambo to CT was at 8pm on 25th Jan 15. Checked in at 6:15pm to be advised by staff that our flight has been delayed by 1 hour due to adverse weather. This was further confirmed by a text received at 7:58pm from Flysafair. Upon check in at the boarding gate at 8:15pm (new boarding time 8:30pm) we were told that our flight had left. Meaning that we \missed our flight". Highly confused and frustrated we approached management to get some clarity. The supervision"