Poor customer service from BA and Discovery Vitality Travel

I booked a flight on British Airways from Johannesburg to London through Discovery Vitality Travel in February 2020. BA cancelled the flight due to Covid and I stupidly opted for a voucher. Now in March 2022, when trying to rebook they say my voucher is invalid !!!! and cannot exchange it for a cash payment. Neither BA nor Discovery Vitality Travel have been able to resolve the issue since I started the process 10 March 2022. I received an email from BA in April 2022, stating that they've refunded my money -, which they've had since February 2020!. However. No money has been paid into my account, and to date BA have not given me proof of payment. Poor customer service from BA and Discovery Vitality Travel with neither company able to resolve.