Shocking service levels

Your service levels are APAULLING, to say the least!! I moved houses on 31st Jan, so I told your staff I need to transfer my account. I then got billed for a cancellation. Eventually, I get a credit. Now I keep getting emails to tell me to return my router or I will get billed. Your WhatsApp agent just tells me to ignore the emails. No, I want proof that I will not be billed for the router that I am USING that you keep telling me to return!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!