Billed Twice in a Month

Hello Peter, I wish to lodge a complaint about the billing and service i have received from Telkom Mobile. My billing schedule is 1st of every month and as per invoice, this is due to be paid on the 6th of the following month. I have been very consistent in paying the bills every month-end, without skipping a single month from contract inception. However for my October Invoice, i was billed on the 1st of October as usual and this was due to be paid on the 6th of November 2017. Without my permission, they decided to run this debit order on the 5th of October 2017 instead of the 31st October for the amount that was due to be paid on the 6th of November 2017. I had just paid the bill for September. The debit order bounced and now my account is on softlock and i have been placed on collections which has affected my credit rating. I have phoned their billing department on several occasions who have admitted to the error but still the problem is not rectified and its been almost 7 days now. Please help