billing me abnormally

good day <br> i have a serious problem with morkels i have took some goods with them and i have been paying my monthly installment but to my surprise each and every month my balance doesnt go down for example last month my balance was R7430 on the 1st of april and i paid R2000 on the 24th and now when i check my balance ther say is R6975 <br> and when i call them to explain to whats going on none of them can explain to me the even hang up the phone for me