Many large and medium-sized enterprises often suffering high long-distance phone spending a month, the enterprise can save money by buying IP card service way, but because of its long user and password authentication, do not have such as call forwarding, busy callback, radio, and new business, such as three-way calling even redial is very trouble, it is difficult to application in the enterprise, and this kind of IP telephony gateway applications, users can completely according to the application ability unceasingly expand voice over IP, \ \ \ "development and upgrade \ \ ", flexible economy,
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