Oh, I understand Comcast is going to insist you have MTA-capability hardware if you're "paying for" voice service (AKA milking the Triple Play promos) so put your own modem w/ embedded MTA on the line. They run ~$90 new, 50-70 used for the basic models on Comcast's approved list. Still come out ahead. Get a model with adequate channel bonding expansion capacity as that's what limits service life & resale value as providers continue to increase bonding.
I hope I'm not still missing something in this discussion. I'm a great believer in not pissing away money on rentals but also cannot be giving my clients bad advice.
.... edit: Tobin
, please verify your modem is MTA capable. I'm assuming either that or the CustServRep looked the other way.