credit card scamers

i have a 0 balance on my credit cards and a great credit rating. But for some reason one of my credit card companies customer service dept. is unable to lower my MOB like interest rate. 21%. i don't know why it makes me so mad. i just wont ever use that card !!!!!!. being a business that relies on peoples desperation is disgusting to me. how is it that people that have no money are charged higher interest rates than those who do. It should be illegal. I also think there should be a class in high school on personal finace. To teach the youth of America the pitfalls of credit. blah blah blah. I'm a bit tense today not sure why.