No customer loyalty

I am very disappointed with standard bank. I have been a loyal customer for the past 24 years. When I received my credit card I was still very young and did not have much knowledge on interest rates. Now that I'm more mature I understand the value of negotiating good Interest rates. I have asked my bank of which I have been a good customer and am currently using many of their services to review my interest rate. I was advised by my banker that this is negotiated when you initially get the card. I am so unhappy with standard bank. When I got the card in my ignorance I was placed on prime + x%. My current rate is high at 21.25%. Never mind that my circumstances have changed and I have been moved to a prestige account all while remaining a loyal customer. I have asked for this interest rate to be reviewed not even to prime but at least to something more reasonable and was advised that this cannot be done. This is so unacceptable. I have proven that I am a good client but standard bank seems uninterested in retaining me a a loyal customer. I cannot believe that 1 mistake seems to last a lifetime. This is causing many people to remain in debt. And even when we try our best to recover we never win as the bank seems only interested in offering more debt than taking care of us to ensure we use debt in a healthy way. I am seriously considering using my knowledge gained and opening a new account at a different institution where at least I can go in with my eyes open. Standard bank you let me down.