Citi - Visa Card Review

I am a good paying credit card customer.  I am generally always carrying a balance, sometimes more than others.  I did business with citi for several years & had a 6.5% interest rates.  I went through a separation and financially, thinks got tight.  I used my credit cards a lot more, but still never went over my limit.  I was never once late on a payment.  One day, I got a bill & my minimum payment went through the roof.  I called them & they said they can change my interest rate whenever they want & they went from 6.5% to 16%.  Needless to say, I cancelled the card!