The application is accessed by clicking a ‘Call Me’ button, which can be embedded anywhere on Facebook that accepts attachments.
Call Me allows users to either receive calls via their PC or to select an existing number on which they would like to receive calls.
The service is optional and calls can be made for free to any user who registers for the service. Users can also set the Call Me button to only be visible to their friends on Facebook.
Truphone chief executive James Tagg said: “The Truphone ‘Call Me’ application delivers real practical value and uses VoIP to bridge social media with regular telephony.
"In the same way that messages on Facebook are always welcome because they are by definition always from friends, phone calls from friends are surely welcome too.”