Router never worked

I purchase a router that has never worked, I have been calling them and sending Emails they said i must do a sim swap, i did that but still, I then asked them to cancel the contract and i was told that its over 7 days ill need to pay 3000 and something then I said no let me carry on with the contract but please fix the router, they promise to send a Corrier guy to pick up the router up until today, I decided to suspend the debit order and my problem now is that I am receiving calls every day asking me to make arrangements and they keep on activating my debit order. please help me how can I resolve this matter because they are ruining my name