Introducing 3CX Phone System 12 – an enterprise-grade software PBX (private branch exchange) meant to meet the telephony needs of both large and small companies. In other words, it is used to create a virtual telephone network, over which employees can communicate via their VoIP phones, PCs, even their iPhones or Android devices. And since all phone call traffic is handled over a local IP network and not by a telephone company, the actual phone calls don't cost a dime. Besides, there is no need to install any additional wires throughout the office, or to expand the company's existing network infrastructure. We've been testing the software for a while now and we can confirm it is worth trying...
Source: http://www.phonearena.com/news/3CX-Phone-System-12-Review_id47609
Source: http://www.phonearena.com/news/3CX-Phone-System-12-Review_id47609