Frastrated customer

Every month I received a sms from supposably woolworths with an x month due on my account, i decided to download the app. Just to discover the installment amount is more than the installment on the sms. I queried the amount at the branch, just to discover i am paying the interest & not the installment... Hence my balance on my account don't change... If I didn't queried the amount i would have never finish paying up my balance. Closing this account!!