To use callback, the caller must first call the callback provider to indicate that they want to establish a conversation and that they expect a callback. Depending on the service provider, various methods are used. The callback request can be made by short call to a special phone number, via an SMS text message, online via a web browser or through special software or an app. The provider then calls the subscriber back on the line from which they want to make the call. In the second step, the participants then give the provider the number they want to call and the provider makes the connection. In general, prior registration with the provider and authentication are required in order for the call to be placed.
Callback is of particular interest when the callback provider offers cheaper rates than the main provider used by the caller. International calls can often be made far more cheaply using this process.