O2 has launched an app which lets users make and receive phone calls and texts via a tablet, computer or smartphone.

Tu Go is available for Android, Apple's iOS devices and Windows 7 PCs but limited to "pay monthly" subscribers - so excludes corporate accounts.

Tu Go deducts charges from the user's existing call minutes allowance, unlike Skype and other chat apps which involve the purchase of credit.

Analysts suggest this billing innovation could prove disruptive.

O2's owner Telefonica has experimented with Voip (voice over internet protocol) before with its Tu Me app which was launched in 2012 with limited success.

However, the earlier program required both parties in the conversation to be using the software, while Tu Go only needs the the caller to have launched the app.

More details you may find in the given link
http://www.bbc.co.uk/news/technology-21623810