Can i use isp modem behind pfsense

[Hakon74]

Hello.
I am new to pfsense, but already love all its features.

My ISP is providing Internet, TV and phone on different vlans on a ZyXEL P2812 modem. I want to remove the modem and have my pfsense in front, but when I do this my phone stops working.

Is it possible to connect the WAN port on the ZyXEL modem to an available NIC and have the ZyXEL handeling the phone?

I have created 3 VLANS on the wan interface and all VLANS recieve differnet IP from DHCP
VLAN 100 = Phone
VLAN 101 = TV
VLAN 102 = Internet

I have tried to make a bridge between VLAN 100 and the unused NIC, but cant make it work. Can this be done on pfsense or do I need a switch or is it not possible at all?