FlySafair / Safair Operations review: Safair payment portal

Have been booking with Safair since their inception using a corporate lodged Amex card. In December suddenly could not use the card for payment. All other airlines, both local and international accept the payment and flight payments go through with no issues. Bank has confirmed in writing that the fault is not on their side, it is with Safair. Safair completely ignore my requests for assistance. I have also tried to pay for flights by contacting the customer support center - this didn't work either. My numerous emails requesting assistance remain unanswered. No communication, no solution, nothing. They obviously do not care about their long-standing customers nor the amount of money being lost as I am trying very hard to book with airlines that do accept my payment and care about their customers.