Credit card question re.: different interest rates - paid first?

[Speedy]

I used a low rate 'courtesy check' on my credit card account. I also have regular monthly charges. I thought the credit card reform law changes required that the higher interest rate balance be paid off first from my monthly payment and then after that is paid in full then the lower interest rate balance is to be paid? My credit card company uses my payment to pay against the balance on the low rate courtesy check first and nothing is used to pay off the regular higher rate monthly charges. I used the 'courtesy check' about a year ago.