<p>Fring is also a free application to be installed on a mobile phone for calls and messages. Calls to other Fring others are free, and are paid at cheap rates to landline and mobile networks. The cell phone models on which Fring works is more limited than for Yeigo. However, Fring users can communicate with users of other instant messaging service like Skype, MSN Messenger, ICQ, Google Talk, SIP, Twitter, AIM, Yahoo etc. Fring also requires a data service plan like WiFi, 3G, GPRS etc. Read more on <a href="https://www.lifewire.com/fring-free-mobile-voip-3426898" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">Fring here</a>.</p>By installing the Truphone software on your mobile phone, you can have your mobile phones routed through the Internet,and make free calls to other Truphone users. Calls to plain mobile and landline phones are cheap. Truphone allows you to make calls through Wi-Fi hotspots and your GSM network, which means you can use it really anywhere. It focuses mainly on high-end phone models like the iPhone, BlackBerry devices, Nokia E and N series etc.Vopium is a mobile VoIP service that offers cheap international calls through GSM and VoIP, without necessarily having a data plan (GPRS, 3G etc.) or Wi-Fi connection. If you do have any of the latter, you can make free calls to other users using the same networks. Vopium also offers new users 30 minutes free calls and 100 free SMS for trial.<a href="https://www.lifewire.com/voip-for-iphone-services-3426661" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">Here</a> is a list of VoIP services that work on Apple&#39;s iPhone.<a href="https://www.lifewire.com/voip-blackberry-3426390" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">Here</a> is a list of VoIP services that work on Blackberry machines.Jaxtr is a nice and completely free service that allows you to make phone calls to and from fixed or mobile phones. You first need to create an account and submit a phone number through which you can be contacted. Then you can call other people who have done the same. The first time, you need to call them through the web interface or jaxtr, then, once you have saved the virtual number of the person on your phone, you can call them from it the next time. International calls are also supported. Note that the phone number you submit will not be seen by other people, but a virtual number will be used instead, assigned by jaxtr.<p>You might be asking why Skype does not come first of this list, with its hundreds of millions of users. While Skype shines in PC-to-PC communication (for how long more?), its presence in the mobile arena only fills a gap in its services. Skype has softphones for Nokia Internet Tablet, Windows Mobile devices and WiFi phones only. Recently, Skype has launched its own mobile phone, called the SkypePhone, which carries all Skype functionalities and services. It is however not yet available in all countries at the time I am writing this. Read more on <a href="http://www.skype.com/intl/en/mobile/" data-component="link" data-source="inlineLink" data-type="externalLink" data-ordinal="1">Skype mobile</a>.</p>Rebtel gives international numbers for your local contacts, and therefore allows you to make international calls at low rates. What you pay is the local GSM fee plus a small fee for Rebtel. You have to type your contact&#39;s international number and Rebtel will create a local number for the area you are in, for you to call them.