Kulula Bad Service

I use Kulula always as my preferred Airline between Cape Town and Lanseria and always book my parents that is very old on Kulula and arranging wheelchairs at both Airports is always a Breeze. This time however it is different. I booked flights for my parents of the 16th of December 2019 for return flights between CT and Lanseria on the 31st of December and have also booked the wheelchairs for both. The wheelchairs was confirmed and the suggest me to call the day before to confirm the wheelchairs. I found early this morning and they said the bookings will be confirmed later in the day and I must call back at 16h00, which I did. Then 1st our call was disconnected and then I call again and talked to Nanwipha. She told me the flight is fully booked and that they cannot help me and my parents must change their flights. This is so unacceptable!!!!. I had to arrange people to take them to the Airport as they are to old to drive, so I cannot change the flight times. I have booked and paid special seats in front of the Aircraft to make it easy for them and to be near the toilet. I have really done everything that I was suppose to do and what Kulula have told me. Lastly the lady that helped me, Nanwipha said that her Supervisor will contact me. Her name is Kathy. I am waiting?