Refusal to refund customer ,worst customer service

Woolworths has the worst customer services ! My mother opened an account with Woolworths and optioned to pay the account via her bank ,since there is no Woolworths store close by . She started experiencing issues with Woolworths when they claimed she defaulted on payments , but she has been faithfully paying her account and has on numerous occasions sent them proof of payments and liaised with their collection department . despite several attempts of her trying to resolve the issue with Woolworths and paying her account they handed over Account to MBD ,who followed up on her case and realized that she was not in default and in addition to that had payed Woolworths more that what she owed .This error was also confirmed by Woolworth's collection department agents who promised to rectify the issue on their side and refund her for the extra payments .all we have been hearing is empty promises from Woolworths on the refund . The agents are rude , harrasing and not helpful at all . we are extremely disappointed with the poor customer service .