This came with my bill: Important Notice of a Change in Terms Effective March 1, if we do not receive your minimum monthly payment in full for 2 consecutive billing periods your APR for purchases and cash advances witll be changed to a variable rate of 25.0%. Pleasse remember that this rate change will only apply if you fail to make your minimum monthly payment by your due date. Otherwise your APR will remain the same. You have the option to decline the change in terms by notifying them in writing. I assume what they are saying is, if you skip a payment or are late. Your APR is going up. You must make a minimum payment each and every month even if you paid more than the min. the month before. And, I'll almost bet that if you decline, they'll close your account.
