Webafrica I've returned the Zyxel, Cannot Get refund of R999

I returned the Zyxel Router at the beginning of March as I'd left WebAfrica. I was told I would be refunded the R999 which they had charged. Instead of a refund, they issued a credit. This is useless as I'm not longer with them. Since that time I've spoken with 4 agents via their WhatsApp line, none of whom could help. The number they gave to phone, I've tried 3 times and always receive the same message 'we are experiencing high call volumes...' the last time they expected a 26 minute waiting period. All I would like is to receive the refund.