Be Warned - this company is bad business

I sent a cancellation via email on 27 July 2022 and received a case number the same day. The debit order for August went through for the notice month. On the first of September I received acknowledgement that the service has been cancelled and immediately after that an invoice for September. I requested them to cancel the invoice as I cancelled the service at the end of July already. I reversed the debit order that went through for September and has been getting threatening emails and sms's that I will be handed over if I do not pay.

I contacted the collections area by phone and the confirmed via email I had been billed in error and that they will reverse the September charge. It will take 21 days to reflect on their system.

I received further threatening SMS's today threatening me with a credit bureau adverse listing. I have all correspondence with Mix Telematics and will sue this company if they affect my credit rating in any way.