Amex Credit Card Complaint

Amex Credit card department,

APR or interest rate New York

My complaint is with American Express, A couple years ago I did the Soldiers and Sailors relief act to get my interest rate reduced with them. Since that time I have made some purchases which are subject to the 9.99 % APR on my Credit Card. I have no issue with agreeing that I owe interest on that amount. What AME- is doing is actually doing when I make a payment, they are increasing my Purchase amount on my Credit card and lowering the amount of the 0.0 % rate. I have not made any purchases on my credit card since -/-/-, and since then they have increased my amount by the interest amount. Nowhere in my bill or Terms of Service does it state that interest is a purchase. By doing this American Express has increased my purchase amount by $50.00 dollars which is subject to the 9.99 interest. Even though I have no made any purchases start from - 2015.