Non-Negotiable Credit Card Interest

So, I phoned the Standard Bank Credit Card division and asked the lady who I should contact to discuss the interest charged on my Credit Card. She rep**** that it is not possible to change credit card interest rate and that Standard Bank does not have a process whereby this is can be discussed or reviewed. She confirmed that I am stuck with the Interest Rate that Standard Bank gave me when I got my credit card more than 15 years ago. So I asked her if my only option is then to go to another bank, and she rep**** that if that is my choice, then I can do that. She can't help me or refer me to anyone, because there is no one to refer me to. She said that I am welcome to phone their complaints line... I can't believe that Std Bank has no process for clients to review interest rates. I have been a Std Bank client for more than 30 years, and I am now getting my 2nd home loan with Standard Bank. So I have no choice but to cancel my Credit Card with Std Bank and then get a card at another bank that gives me half the interest rate. Really. Half. Std Bank interest = R20%. Capitech is 10.5%. This is really poor service and I am very disappointed about this lack of loyalty to long-term clients. It will be very inconvenient for me to bank with two different banks, but if is saves me this much money, I have no choice.