Fradulent alteration of my discovery credit card agreement terms by an FNB call taker

On the 22/07/19, An agent from the FNB call centre **********ly altered the agreement terms on my contract resulting in the cancelation of my straight facility on my credit card! I have been making payments form July 2019 into this account and I notice that all my payments resulted in a negative balance. When I tried to resolve this matter, I was thrown from pillar to post and I was even denied access to the transcript of my conversation with the call centre agent.