Dissatisfied with Mango Airlines

I had an international flight booked on 9 April 2020 from OR Tambo Airport to Indira Ghandi International Aiport in Delhi, India. I reside in Durban so I booked a flight with Mango airlines on 9 April from King Shaka International Airport to OR Tambo. In light of the coronavirus problem, India suspended travel visas so unfortunately, I cannot embark on my international flight and therefore, my local flight from Durban to Johannesburg on 9 April is pointless. I had to move my international flight to September 2020. I called the Mango contact centre and explained my situation and advised that I needed to move my local flight to September 2020 as well. The operator mentioned that there will be a change fee. My question is….how can Mango charge me a change fee when this is not my fault and not even my choice to make this change? I am forced to make this change because of the coronavirus situation. Upon returning to South Africa from India, my return flight to Durban from Or Tambo with Kulula was handled very well. The change fee was waived with Kulula. Why isn’t mango helping its customers with waivering of change fees during this problematic and stressful time? I am really disappointed with the service that Mango Airlines offers. I think this is a total ******* because after paying for my flight, I now have to pay an almost similar change fee and this isn’t even my fault or my choice.