We’ve been using the rental Modem from Comcast and paying $10 a month for the last 5 years. This year resolution was to buy a modem that works with voice and internet to replace the old one we’ve been renting. I’ve heard so many problems of people trying to replace the rental unit due to compatibility. I bought Arris TM822G from Amazon, there’s great instruction for Self Activation Process which I used and it went without a hitch at 11PM at night.