BAD SERVICE FNB DEBIT DEPT

I have lost R899 because FNB don't want to investigate the refund and claim had a deal with Microsoft,send FNB the invoice from Makro that i bought microsoft office 365 home cash but still FNB claim i had the debit order agreement with microsoft of R899 , feel like FNB is working with Microsoft to ***** my money since can't get refund and paying for a big company that ***** money from the poor black person.