Multiple Debit Orders

I took out a contract with Vodacom last month.

All went smooth, on the 29th of August 2018, they tried to debit my account which failed because I only get paid the last day of each month.

I then called Vodacom and Promised to to pay by 30 Sep 2018, then on the 10th of Sep 2018 another debit order of R659.37 bounced from my account.

When I called them the lady who was helping me told it was so high due to the 2X penalty fees for the debit order bouncing.

I was not aware of any penalty fees, and how is it possible for a contract of R 119.00 pm to suddenly climb to R659.37 ?

I do not understand why they tried to debit order the amount again on the 10th of Sep after I have promised to pay by 30 Sep 2018.

Utterly disappointed with the service received from Vodacom.