Cancelling flight flights with no notice

Kulula advertise 20h00 flights, and cancels with no notice despite having mobile numbers. I've had 2 Wednesday flights in 2 months booked for 20h00 and when receiving flight confirmation 3 days prior I notice that the time is changed with no notice to 17.10. No message has been received. It looks as though Kulula are advertising late flights but are Cancelling. <br> It is not possible to fly this early. There are no other later flights on Kulula or British Airways for the later slots. This is unacceptable.