A free app for Android, by Digitelecom.

Applefone Vox is an Android application that allows you to make VoIP calls using your mobile device. It uses 3G/Edge/Wi-Fi Internet connectivity to make the calls, and you can choose to use your mobile data or Wi-Fi for making the calls.

The app has been developed to be compatible with the standard SIP protocol, which is the main protocol used in the communication of voice calls. It also has the capability of supporting the G729, PCMU, and PCMA codecs.

It has been developed with the user interface of the Android platform in mind, which makes it very easy to use. The app also has the capability of running behind the NAT (network address translation) or private IP address.