You don't need any static routes in the IP Phone if you're directly connecting it to a port with VLAN 660.
Just put the VLAN 660, voice WAN profile static IP, set up the SIP profiles and that's should be it, in most cases.
Now, as you're facing an issue with outbound calls, ensure you're prefixing a 0 to the numbers you're dialling, which you most likely are.
Secondly, check if the IP Phone has ALG settings and try tweaking them.
What make is your IP Phone, BTW? If it's Grandstream, set the NAT Traversal setting to Keep-Alive and check.