Betway not paying out

I won over R1 million on Betway. I withdrew the maximum of R1 million. I waited the 3-5 working days. No funds. I checked my emails, WhatsApp messages and messages on the Betway platform. No communication. I eventually saw that the funds had been returned to my casino account. I called my 'account manager', who eventually took my call. He informed me that I had not provided a bank confirmation letter, which they did not communicate to me. I provided the letter. Waited another 3-5 days, nothing. Once again, the funds have been returned to my account. Still no communication. I have tried to call this account manager, he is not picking up my calls, even though I can see that he has been on WhatsApp after I have messaged and tried to call him. Help! This is not right. It seems that Betway is doing everything to avoid paying me what I rightfully won.