Multiple vlan single interface transparent proxy

[fusi0n]

Hi everyone, am new here.

My ISP sends out packets that are VLAN tagged for both 10 and 20 within the same WAN interface.

Current setup

ISP sends packets with VLAN tag 10 and 20
v
v
(WAN)
--------
[Router] 192.168.1.254
Configured by ISP to assign VLAN tags to respective interfaces
--------
LAN Port 1 (VLAN 10) > Internet
LAN Port 2 (VLAN 20) > VOIP phone

I'm trying install a 2x NIC pfSense box before the router:

ISP sends packets with VLAN tag 10 and 20
v
v
LAN Port 1 (VLAN 10)
--------
[pfSense] 192.168.1.1
--------
LAN Port 2 (VLAN 10)
v
v
(WAN)
--------
[Router] 192.168.1.254
Configured by ISP to assign VLAN tags to respective interfaces
--------
LAN Port 1 (VLAN 10) > Internet (Working)
LAN Port 2 (VLAN 20) > VOIP phone (Not working)

If I assign VLAN 10 to both LAN 1 and LAN 2 in pfSense, I can access the internet without issue. But it also means I am unable to use VOIP because VLAN 20 tags are not being forwarded.

How do I configure pfSense to forward all traffic from LAN 1 to LAN 2 regardless of VLAN tag, so I can get VLAN 20 tagged packets?