Kulula the Worst!!!

Kulula is the worst airline ever!!!! I made a booking for the 13 June 2021 on the 16H20 flight from King Shaka to OR Tambo, on arrival at the airport i was informed that my flight is only at 20h20, i have screenshot showing my booking. On investigation it showed my flight time has changed without my knowledge...how is this possible?? On asking them at the help desk to fix this problem i was told to pay an additional R1000+ for two tickets, and the manager on duty was extremely unhelpful, i have her name as reference...when i showed her the screenshot of my flight times, she simply told me that no seats was available on the 16h20 flight, yet a few minutes earlier the helpdesk agent wanted to sell seats to me....Kulula this is absolute poor service!!!