Bad service

My mother has Woolworths account she's 65 yrs old on pension. My mother owes Woolworths about R2000 or maybe R2200 which her installment of R170 a month. My mother has been paying R300 every month for about 8 months without buying anything, but my mother still owes R2200 the balance doesn't change. She went to Woolworths store Umlazi mega city branch to pay for this month again and asked them why the balance doesn't change, why she has not received a statement, why no one can explain this?.... Bo one could assist. Woolworths staff could not an elderly to explain why her balance is not changing. They called their customer service they told her she has a monthly interest of R90 monthly. But, her other question is she's been paying more every month without fail🤷🏽 ... Woolworths if there was an option of negative stars on this review I would give you the highest negative number 😡