Telkom Billing me for a service I did not use

On 31 July I put in a request to cancel my LTE service from Telkom. My reference # was given to me as ********** 9 and an e-mail was sent to me that my service will be cancelled on 31 August 2018.

Low and behold, 1 September 2018 my service was still running. I did not use any of the data and sent Telkom another e-mail to explain why my service was not cancelled. Eventually, the service was cancelled.

I received an invoice yesterday afternoon (04.09.2018) and I received a bill of R8.49..... Now my question is: "for what?" I did not use the service on that day, I did not ask to have the service for that day, as my cancellation clearly states 31.08.2018 and it was confirmed as 31.08.2018.

I want this to be rectified immediately as this is not my fault.