I want to remove Xfinity WiFi Gateway from my list of wifi equipment so that I can try to activate my external modem/router

I would like to remove my Xfinity WiFi Gateway device from my list of wifi equipment because I want to activate my own personal modem/router. I was having issues activating my personal modem/router, so I tried the one they sent me (which I didn't ask for), and it worked. But I want to activate the personal one I bought to see if it works, but there is no way for me in the app to activate a second personal device, so I thought I'd try disconnecting/removing the Xfinity Wifi Gateway to try again, but unfortunately I'm not able to do that as well. Any help is appreciated.