British Airways e-voucher/refund

I brought return tickets from Cape Town to Durban for the Comrades which will be held in August 2022. BA was grounded and I have received an e-voucher. I cannot use that voucher to any flights and it will expire on Sept 2023. I have spoke to BA in United Kingdom and they said, once an e-voucher is issued, it cannot be reversed for a refund. I need a refund on these tickets as BA has been grounded. :-(