Office Ext app for iPhone and iPad

Office Ext - iPhone Edition is a SIP-based phone for Apple iPhone and iPod touch that uses a Wi-Fi or cellular data network connection to make and receive calls.
Using the iPhone or iPods existing contact list, Office Ext iPhone Edition facilitates easy and effective communication management with an intuitive interface that accommodates multiple calls. Call functionality includes the ability to swap between two calls, merge and split calls and perform attended and unattended transfers.
Office Ext - iPhone Edition incorporates advanced security settings which allow for secure call signaling and audio encryption. It also contains enhanced audio features including G.711, G.722, iLBC, GSM, SILK and Opus.
Bria iPhone Edition is a superior iPhone VoIP application for Home Box Office as it is used as an extension to its PBX system.