Unauthorised Debit

I took delivery of my new router on 4th December. A debit order was processed on my account on the7th of December without my authority and without any notification to me. My debit order date is the 28th of the month. This has resulted in an unpaid debit on my account and unpaid debit order bank charges. I phoned Cell C on Friday to have this rectified and was told that a call will be logged and to date no one has contacted me. My bank account is now in a negative because of this and I am still awaiting feedback REF: ********** 350