BILLED TWICE IN ONE MONTH !!!

I upgraded my cellphone in the middle of September 2017 at the Telkom branch in the Woodlands Mall. I upgraded to a package that was R100.00 more. During the process of upgrading I asked the consultant numerous times what the payable amount will be on my next statement. He confirmed that it will only be the amount of the new contract. In the middle of September the debit order went off for my "previous" contract which I understand. On the 4th of October 2017 I received my statement and saw that the amount to be debited from my account on the 15th of October 2017 is almost double my new contract fee. I went back to the Telkom branch on the same day where they told me about a "pro rata" policy and that I was charged the whole amount for September on my "previous" contract and pro rata for the rest of the month of September and in full for the month of October. This is nonsense. The consultant was negligent in that he did not tell me about this "pro rata policy" even after I asked him specifically what I will be charged on my next statement. I kindly request that this be rectified as it was not negligence from my side but from a member of your company.