Refund Mango Airline

I wanted to cancel my flight last year 2019 and was told to rebook another flight or get a voucher. I changed my flight to Easter weekend 2020. I then received an email to say they are not flying to Lanseria anymore and I can fly to OR Tambo. This was very inconvenient for me and I insisted on cancelling and getting a refund. On the 26th of March I was told that I will get a refund. Today the 12th of May 2020, I'm still waiting for my refund, after numerous reminders and trying to phone, no-one ever answers the phone. I don't know what to do anymore.