@BraswellJay
Do you mean which physical interface in your router?
Not exactly sure what you mean by "new WAN interfaces"
The SIP traffic will use the interface assigned to the gateway address your are providing the phones, either static or DHCP.
No Audio is almost ALWAYS a NAT issue. Look at your NAT settings on the old interface and compare them to the new interface.
What make and model router are you using?