Billed on a faulty device

I haven't had internet connection for almost a month now. A device stopped working after 10 days they debited money from my account. I've spoken to two consultants already named Vangeli and Sbusiso Tuli whom made empty promises about sending a technician who will come and replace the faulty device and downgrade my subscription to the 5G of R499 but until this day nothing has happened and yet they still bill me for services not rendered. I'm a very angry and upset client where I am!!!