Dishonest customer service and fees

I am very dissapointed. I have an arrears charge on my profile, which was created when i cancelled a service with them. I should not have been charged for this as this fee only applies if you used the service. I am stuck with a TP link router that I do not want, and their courier never came to collect the router. I have been complaining about this to them since last year, empty promises and no results. when I try to get a new fibre line ordered I am blocked by this charge which is not my fault, and they always escalate but no one reversed or erased this charge. I have been without internet since last year and requested assistance but every time i chat I have to explain the whole story again with more empty promises. Even now, I am told that there is an active line at my premises, but their agents keep confirming its cancelled. Why am I the client being punished for such horrible dishonest customer service.