How do you complain if your credit card company breaks the law?

I have a credit card that the due date is always the 2nd of the month. With today being the 1st, I went online to pay the bill so it wouldn't be late. They charged me a rush payment fee. (This is not the first time they have done this.) I believe they have violated the new credit card law because it says that your bill has to be due the same day of the month and if that day is on a weekend, they can't charge you a late fee until the following business day (which in this case would be Tuesday). But when I went online to pay, they told me I had to pay the rush fee today (the 1st) or there would be a late charge to my account. Obviously I am paying the card off the next time I get paid and never using it again, but I'd like to turn them in for violating the new credit card laws. Anyone know how you do that?