Attempting to help by clarifying a couple of things that I saw from an earlier post that has since had the comments ability turned off.
This unit does not contain what we Xfinity users have come to know as eMTA jacks on the back to handle voice service directly from Xfinity.
I used to have Xfinity voice service but several years ago migrated over to Ooma. The Ooma device, depending on which model you have, will either be ethernet only or ethernet/wifi. I just activated my G54 unit last night but have already found that my Ooma device, connected by ethernet cable to one of the ethernet jacks on the back of the G54, is working as expected for both incoming and outgoing calls.