Unauthorized bouncing debit order charges on my statement

Vodacom is very great when it comes to addressing issues. Great service BUT!!!!!

I pay directly at the store and this month I incurred over R100 in bouncing debit order charges. This is very alarming as Vodacom doesn't debit me per our agreement. I pay at the store directly. Why is there a debit order and how did It bounce cos I just got paid, but the alarming thing is how come there's over R100 in penatiles and interest and what if one day you decide to debit my account for no reason? Please address this issue before my contract ends as it's very alarming to think there's an unauthorized debit order taking place from my account from VODACOM.

I hope this matter will be addressed swiftly. I o ly paid what was due from me this month and non of those bouncing charges and they are unauthorized.