Sipmobile

Main features:
Free calls to US and Canadian numbers.
Free calls to more than 2000 VoIP networks.
For instructions please visit https://www.sipmobile.org/wiki/wiki/how-to-call/
Audio/video calls.
Online and offline messages.
Push notifications for longer battery life.
Secure communications with cryptographic software.
Supports modern codecs (Opus, WP8) for better audio/video quality.
Picture sharing.
Compatible with Sipmobile soft phone for iOS and Windows Phone.
Inside Sipmobile domain you can use Self-Administration service.
This service allows you:
view recent calls.
use click-to-dial service.
manage voicemail (Voice mail number is 2000).
maintain your address book.
set call barring for incoming and outgoing calls.
set your personal alarms.
manage your account password.