Disgruntled customer

I just want to write how disgusted I am at the service I have received from Supersonic. I have been with them since 2019 and every month I pay my account via EFT. Recently I have been handed over for debt collection due to an unpaid debit order which I have never ever approved as I do not like paying via debit order. I want to make one thing very clear, I have paid my accounts and all proof of payment has been send to the debt company as well as Supersonic showing account has been paid. I even upgraded my fiber line as was supposed to be paying the promotion amount but they are still invoicing me for the full amount which has all been paid. I will be taking this further if I do not get feedback from one of the senior managers and my name be cleared. There is so much incompetence happening and it is really starting to get me very frustrated. Supersonic better get their accounts right as they will start losing customers if they carry on like this.