So your pfsense wan network or transit is on 10.0.0/24 what is psfense IP?? You can for sure point to different gateways on this transit network that your calling your wan.. There was recently a thread about this..
"Pfsense will not let me add 10.0.0.1 interface since it's in the same subnet as the other gateway"
I think your confusing terms here.. If you have an INTERFACE on pfsense that has IP address 10.0.0.1, no pfsense is not going to allow you to create another interface with IP address 10.0.0.2.. That is not a GATEWAY..
If your running the phones and data on the same network.. And you want phones to come in and hit pfsense on .2 vs .1 - then that would just be a VIP you create on that network..
Why are you running data and voip on the same network.. That is a BAD idea.. Your data and voip should be on different vlans plan and simple..
You should never use more than 1 network on the same wire.. If you can not do vlans – get some vlan capable switches and do it correctly!!!