Again, its the modem for the phone. I didn't rent that and as you say i don't have to pay for it. How do I get it back to them once I terminate the service?
What happens is you keep their unit partially active, even after you activate your own modem and router. The one that they supplied you with, that is probably a modem/router/telephone adapter combo. when you activate your own modem and router (I recommend separate units) those portions of TW's equipment will be inactive, but the telephone portion will still be active. You will keep using it and it will not cost you anything as long as you are only using it for telephone. You use your own modem and router for internet. I recommend the SB6183 as a modem and any decent AC router with good ratings on amazon.