Debited Twice - Vodacom not able to reslove!!!!!

Vodacom normally debits my bank acc on the 20th of each month with R358-50. On 20 Sep Vodacom did not debit my acc. I queried them on 22 Sep. They advised that there was a system issue and they will debit me on 25 Sep, which they did. On 29 Sep they debited me again with the same amount. I called the call centre who logged a query ref no: S3-9JL1E-EVNFN to refund the one debit. Called them again a few days later as I had received no feedback. They advised me (call ref no:***) to reverse the debit order at my bank. I then contacted my bank to reverse the debit order. on 11 Oct I receive a sms from Vodacom's collection dept stating that I should contact them icw a returned debit order. I phone them and speak to Lerato Klaas. I explain the whole situation to her. She then informs me that I will be charged R100 for the returned debit order!!! Yet she also confirms that my account is NOT in arrears. I explain to her that I returned the debit order as instructed by Vodacom. She then logs a displute for the R100 for which I have not received a response to date. How can I get this SIMPLE matter sorted out, as this whole matter was not my fault and yet I am inconvenienced by this!!!??