Kulula.com owes me money

I booked return flights to Johannesburg in May 2020 for a course I was meant to be attending. However, due to the Covid-19 pandemic, the course has since been cancelled. I therefore need to cancel these tickets. Furthermore, I am a frontline medical doctor and will be expected to be working during the period that the flights have been booked. I kindly requested to cancel these flights and be reimbursed. I have thus far received no response. Pathetic service and no one picks up the phones!