Bridge mode

I have had the Comcast Business gateway in bridge mode for a few years. Yesterday, my internet stopped working. After calling support today, my internet was restored. The agent changed the gateway to IP pass through. I told her I wanted bridge mode, as I wanted a direct IP given to my firewall. She said it wasn’t possible, as internet wouldn’t work. How is this so? I’ve had it in bridge mode acting as a regular modem without issues for many years. How is this suddenly not allowed? The gateway is now handing out a 10.1.0.x address to my firewall. I prefer to have a direct Comcast IP. I have dynamic IP address, no static. When I change the settings on the gateway, internet does indeed stop ✋ working. Help!