Can I use a rented voice modem with a user owned data modem

Subject pretty much says it.  I have two modems using a splitter: a voice modem is rented from Xfinity for the Voice service and a data modem (user owned) is used for ... data.  I want to replace the data modem with a newer, DOCSIS 3.1, high speed modem.  Can I use the old voice modem and just swap out the data modems?  

I realize that replacing both the modems at this point with a new voice/data modem would save me the rental fee of the current voice modem but there are no voice/data modems available that are on the current Xfinity compatibility list.  If I can upgrade the data modem, I can get better data speed (since I am currently paying for it but cannot take advantage of it with my current DOCSIS 3.0 modem).  I am trying to verify my options before I proceed.