Vodacom decided it was ok to debit my old bank account without my authority!!

Vodacom debited my old FNB bank account on 25 June, without my authorisation, and subsequently, the debit order bounced. I phoned into the contact centre and they confirmed they only have my new bank account number. Attached is proof of the incorrect bank account being debited. Please ensure that you debit the correct bank account, and also refund the R100 unpaid fees charged to the old bank account, which is now in overdraft. Provide details of how Vodacom decided it was ok to debit my old bank account without my authority as all the other months' debit order went through fine on the new correct bank account. This is serious and definitely not TCF!