Unpaid Debit order

I resigned from my previous employer in August where I sent a request via Vodacom's website to change my banking details.I received no response. I then sent through another request advising them that I will no be liable for any extra costs if the debit order does not go through. I closed my account and no debit order went off my new account. I phoned the call centre where they promised to debit my account the following week which was never done. I then received an sms on 4/12/15 to advise of the unpaid debit order where already I had phoned the call centre. On 5 Dec 2015, I got an IVR message ,confirm by pressing 09 for the debit order to go off on the 9 December 2015 (which I accepted).On the 12/12/15 I received another sms stating'Thank you for commiting to a payment arrangement on your Vodacom account. Your payment is due on 9 DEC-15. ' Yesterday (9 Dec 2015) I received an sms stating 'LIfe is hectic so just a reminder that R318.50 is due today as per your agreement. Please ensure that funds are available if arranged debit order.' Debit order still did not go through. Now I am requested to pay a penalty for all this. I'm so disappointed.