unfair banking practice

I have received an unfair banking practices during my home loan application, I am self employed and when I made my application to Standard bank via a bond originator, my initial application was refused,on the ground that in one month I did not make deposit into my personal account, which was clear on the bank statement that the aforesaid payment was made on or before 15th of the previous month and therefore, enough funds were available for monthly expenses, on the reapplication, the application was approved in the spirit of a favour and now I was classified as a high risk client, likely to default in one or more monthly payment, and my classification meant I was going to pay interest on a scale of higher plus. I was advised through my bond originator that the rate could be revisited depending on my payment behaviour after 24 months, I accepted that then as it sounded fair then. Recently with the war in Ukraine, I had requested the bank to relook at my interest rate and readjust them, in response, Standard bank informed me that my interest rate cannot be readjusted because once the rate is fixed it fixed it cannot be adjusted, which I found to be unfair and discriminatory on the basis on affordability, because I have never defaulted on my obligation to pay monthly payment and my financials have been consistent. Very disappointed and this is not in the spirit of the National Credit Act, which promotes fair and just