Callingbell is a mobile dialer or application which makes VoIP calls with minimum iOS version support of 6.0 on Apple iPhone, iPad and it uses the 3G/Edge/wifi Internet connectivity. Callingbell is developed based on the requirements of VoIP Providers business needs. Features :- Callingbell uses SIP protocol based for signaling. Callingbell Supports all codecs. Callingbell run Behind NAT or private IP. User Friendly Interface. Auto Sync of Balance. Real Time Sip status messages. Call History. Loud Speaker. Hold. Address book integration. Compatible with all sip standard switches. It has very efficient implementation of jitter buffer to play voice smoothly.