Refusing to lower credit card interest rate

STB absolutely refuses to lower my credit card interest rate while unable to provide me with reasons as to why.

I received my credit card many years ago at an interest rate of 22-23% when i was still studying. Since then I qualified and is a professional member of a regulatory body. According to STB's own mobile app, my credit score is 704, exceptional and stable, yet still they refuse to go below 18%. I requested my risk profile STB has of me that determines the 18%, so that I can improve on whatever it is that is supposedly making me risky (but nothing provided). How can I only be slightly less risky now than I was when I was a student doing articles? Yet STB will be quick to assist in increasing your credit card limit so they can benefit from you making more debt.

A colleague of mine also banks with STB with an interest rate of 12%. Even on the website it says it can be as low as 11.75%. My wife is a sole proprietor and as a NEW client at Capitec, she received a 13% credit card with the same credit limit as me. I have banked with STB for 20+ years and I feel like theres no benefit to being loyal to STB anymore if it does not care about its clients in return.

If STB cannot either give me a valid explanation, or an actual reasonable interest rate, I will move over to Capitec as that will just make more financial sense, and furthermore, I will warn anyone against STB's credit facilities.