Very POOR customer service

Due to the recent state of emergency declared by the president we where forced to reschedule our flights from Cape Town to JHB. However we could not do this on Mango, so we had to rebook and now they don't want to refund our original tickets we are now stuck with 4 tickets from Cape Town to JHB. I have tried to plead my case to Mango customer service but there is just no answer at one stage i held on for 1 and a half hours to no avail. I understand the no refund policy but i am sure an exception can be **** under the extreme circumstance.