If you are facing one way communication issue (You can hear the people you call, but they cant hear you or vice versa) then please check that you have done the port forwarding on the modem/router for VoIP traffic properly.
You need to forward port number 5060 to the IP address on the V220 VoIP phone. Please note that you need to configure the static IP address V220 VoIP phone.
To configure port forwarding on modem/router, please refer to it's user manual.
For more information on Port Forwarding, please visit www.portforward.com.