Please change your router configuration about VoIP:

Select [Configuration] è [VoIP] è [Service Provider]
1. Registrar address : 217.14.132.172 Registrar port:5065
2. Proxy address : 217.14.132.172 Proxy port:5065
3. Outbound address : 217.14.132.172 Outbound address: 5065

You can use another way to do easier setting.
Select [Quick Start] -> [VoIP]
Registrar address : voiptalk.org Registrar port:5060