Change of banking details

I have changed my banking details with Vodacom just over three months ago. For the past three months you have not debited my account and I got notices of late payment. This month the debit order dit go through, but for a mere R11 and my bill is way more than that. I am very concerned about the effect this may have on my credit record. <br> <br> I would like a competent person to contact me to rectify this matter,