American Express paying double interest Los Angeles California

hey american express customers... is this happening to you? I open a american express account about a year and a half ago.. I made a balance transfer at a great 3.99 interest rate, always making my payments on time and always more than the minimun payment, but I made a mistake , I made a few purchases, nothing crazy, about 1300, at a interest rate of 8.99, after they raise my rate to 11.24 I started to pay attention to my statements and the payments I make go towards the balance tranfers at 3.99 interest rate and nothing goes to my purchases...

here is the ripoff I get charge interest on my purchases at 11.24 and interest on my balance transfer a 3.99, my payment takes care of the finance charges on the two balances but the finance charges on my purchases get add up to my purchases balances every month, so even if I make my payments on time and more than the minimun my purchases balance goes up every month and I wont chip away on this balance until I finist paying the balance transfer... is this fair?...is this legal?

Salvador
Fresno, California
U.S.A.