********* behavior

I have a home loan with Nedbank and last year December the date of the debit order fell over the Christmas period so I missed the payment.I made an arrangement to pay the money over a 3 months period and this month they double debited my account.The money they took us for my daughter’s school fees which is 3 months behind already.This is definitely unacceptable and they can’t just take money from my account as if they are the only creditors I have