Poor Customer Service at National Security and Fire

I used to be a client of National Security. I returned 2 radio transmitters physically to their office in Florida Park Johannesburg end of April 2022. However, since then the call centre in KZN continues to charge me monthly for their transmitter even though I confirmed with the manager in their accounts department that the transmitters were returned. Not sure why I am being treated this way but it shows the lack of communication between the KZN office and the satellite offices in Johannesburg. Why should it be my responsibility to prove I have given their equipment back to them and I have to constantly call every month to explain I have given their - poor communication, poor service delivery, no respect for their customers!