DEMAND DEPOSIT not Authorised

I took a iPhone XR on contract from FNB Fussion and paid it off up until end June 2026. Contact them asking when was the last payment and that I would not owe them anything. So this month they decided to debit my account with R89 on 31/08/2026 for...DEMAND DEPOSIT! *** is that? I called in earlier today and spoke to a lady (who I enquired with in June what the procedure was in June) as well as today and was told they will keep on debiting me till I cancel it...according to who? And I should have a reference number? No reference number was given in June? So FNB Fussion will just keep on *****ing R89 from me till I say stop....Interesting! And I must now wait 48 hours after disputing the debit order????