Voice Over IP lets you make phone calls via the internet Linphone is a smallish, open source project which aims to provide that service for free. This very capable software can be used on almost all mobile and desktop devices and offers HD video and audio calls, conferencing, picture and file sharing, echo cancellation and more. You can store contacts and it has a very clean, user-friendly interface. However, since Linphone is open source, it doesn’t have the full support of larger programs.