ChaiyoCall

ChaiyoCall enables to make VoIP calls whenever your device is connected to the internet through WIFI or 3G. This app is simple to install and very easy to configure. Featuring a comfortable and simple user interface ChaiyoCall sip client lets your connect your phone to standard landline or mobile phones.

Features:

SIP protocol support
Making and receiving calls
Codecs supported: G729, G722, G711,GSM
Call timer
Recent Call
Phone Book (Synchronize with Phone Address Book)
Add contact from App
Local signaling (Dial tone, busy, ring back, etc.)
Redial
Speaker
Mute
Touch Tone
Silence Suppression
Echo Cancellation
Registration Timeout
Proxy Setting
STUN Server

System Requirements:

Supported : iOS 7.0 or later.This Application is optimized for iPhone 5.
Internet Connectivity: Wi-Fi,3G.