Cash for voucher not acceptable

On the 15/01/2020 I booked a trip to Bali with Cathay Pacific for myself, my wife and a friend, because Cathay Pacific only flies from Johannesburg I booked flights to Johannesburg from Cape Town and also returns after our two week holiday. I paid in cash for these flights. Due to the worldwide pandemic flysafair and mango cancelled our flights which were due to depart on the 08/04/2020,these airlines want to issue a voucher for these flights, a voucher which is only valid for 6 months and non transferrable. Our Bali vacation is cancelled and we intend to reschedule next year some time. I have contacted these airlines several times and all I get is an automated message every time. I can not use the voucher at all,since we no longer have any reason to go to Johannesburg and effectively I will have lost all this money due to no fault of my own. This is simply unfair since these airlines can be reimbursed by the government and even in some cases have insurance. what recourse do I as consumer have. Why must I get a voucher when I did not pay with a voucher, credit card or coupon. Please help