Poor service; return router upon cancellation, even after 12months partnership

I cancelled my contract with them after I got tired of being disconnected many times due to their fault billing wrong account every month. You can't get through to them and they don't have a contact number, only for sales. They make use of WhatsApp and emails to communicate which is extremely frustrating especially when you have queries and issues. On cancellation they want their router back, like brand new condition, how is that possible after 14 months. That's ridiculous...with other service providers, giving better service, you own the router after 12months and they are way cheaper. "If you cancel your service you will be billed for your router, or you may return it to us in its original condition and packaging."...what ____ is this?