Is there a way to connect a phone to a modem that does not support voice systems?

I would like to use xfinity's voice service but the current modem we have does not support voice service (netgear C6300v2). I'm struggling to understand how this works. I'm curious if there is an adapter that I can connect to my modem that would also connect to my phone that would allow me to use voice service? I'm trying to avoid purchasing a new modem when my current one is less than a year old.