Okay, I've done some checking because I also have TWC and am tired of the modem lease charge.
From what I understand you can buy a modem for about $35 to use, but you have to keep the phone/internet modem in order to use the phone line. However, you don't have to pay a lease fee on the phone modem. You keep that modem, use it for just the phone, and there's no rental charge.
If you can figure out the sense in that kind of arrangement you're a better man than I. I'm ordering my new modem and getting rid of this rental fee.
Here's where I got the info:
TWC explanationOne of the modems they have on the list is available for around $33. Oh, this is a DOCSIS 3.0 modem.