The most popular VoIP (Voice over IP, IP-telephony) program. You can call to any Skype subscribers over the Internet, which can be anywhere in the world. It is possible to call any mobile and landline numbers to any country in the world with very low rates (much cheaper than directly). In this case Skype provides excellent call quality (better than in ordinary phone, and good for dial-up connection) and full confidentiality by encrypting the signal. Also, Skype allows you to send SMS (Sms) messages, and supports the video calls in a videoconference.
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Syphone - Version 0.99b11.
This application lets you view, save and send SMS messages.