Call4UVOX

Call4U is the Mobile Dialer that allows to make VoIP calls from any of the android devices and it uses 3G/Edge/Wi-Fi Internet connectivity. It is developed based on the requirements of VoIP Providers business needs.
Call4U Features:-
It uses SIP protocol based for signaling
Supports G729, PCMU, and PCMA codecs
Runs behind NAT or Private IP
User Friendly Interface
Auto Sync of Balance
Real Time Sip status messages
Call History
Address book integration
Compatible with all sip standard switches
Call4U has very efficient implementation of jitter buffer to play voice smoothly.
Silent suppression and comfort noise generation has been used to reduce the bandwidth usage, and this makes the dialer more efficient in making VoIP calls.
It easily integrates with mobile phonebook and auto detects (+) sign when contact is picked from phonebook.”