***** case unresolved at my expense??

I settled my credit card (after not using it for a year)and requested that the account be closed. 3 days later I checked the account and it had been maxed, ***** case was logged no communication received at all until I followed up to heard that the refund request was declined as transactions were approved through an OTP sent via text to a number I no longer have access to and my OTP is not received via SMS either? Strange? Numerous escalations with detailed dates and proof however it seems to get sent back to PVT banking and stops there. I have given Standard Bank until the 22nd April 2020 to resolve. Should they not resolve and refund me all costs including interest charged I will be walking away as I take it they have agreed to write off all debt.