For years, software providers have offered ways to make free calls from cellphones, and most of them even work. The problem is putting the software on your phone.
It is not that carriers want to make it hard for subscribers to load Skype, Fring and other free-calling apps onto phones, although the networks obviously bristle at the idea of giving their customers a way to make free calls (also known as "voice over Internet protocol" or telephony). The bigger issue is that until recently, carriers have made it painfully hard to load anything onto your phone, whether it is sophisticated software or a simple ring tone.
But since Apple buried its spurs in the backside of the industry by creating an application store that actually works - thereby compelling other companies to follow suit - these free-calling applications are almost within the reach of the average smartphone user.
Of the many free-calling applications, Fring, a start-up based in Israel, and Skype, the standard-bearer of the free-calling realm, are among the user-friendlier. But even then, the applications are not yet worth the inconvenience unless you plan to make a fair number of international phone calls and can put up with less-than-perfect call quality (or far worse).
Here is how it works: It helps to have a device that has Wi-Fi, because the call quality is best when carried over the Internet, not through the carrier's pipes. (Skype offers a version that works with a smartphone's cellular-data connection, but it says it "can't guarantee voice quality" for those.)
Once the application is loaded and started, the software typically displays its own keypad. As long as you are in a Wi-Fi hot spot, you can make free calls directly to other members of the particular service - Fring-to-Fring calls, say, or Skype-to-Skype. Or you can call landlines through Skype at cheap rates once you have a prepaid account.
Skype and Fring users are assigned ID numbers or names, and when they are used for dialing, the calls go over the service's Internet servers. If a telephone number is used, instead of an ID number, the call is partly routed over phone lines, then to Skype's Internet servers, which hand it off again to a local carrier to connect the call on the other end. That is why users see strange local numbers on their caller ID for incoming calls, rather than the name or number of a friend.