Supersonic overcharging us and ZERO customer service assistance.

Supersonic has been overcharging us for almost a year, for Plumes which we DO NOT HAVE! We had them for a 7 day trial period in April last year, but they did not work so we returned them (Darrell the technician fetched them in person) and we have been billed for them ever since, despite my numerous emails, Whatsapp’s and calls to try and resolve it. I tried to Whatsapp again last week and was told “Someone will assist you shortly”. I am still waiting. Sent another WhatsApp today, no response at all. And nobody is answering the phone. So I do not know what to do anymore, besides canceling our debit order? Maybe that will get their attention. Or maybe they will just cut us off?