UK mobile phone operator O2 is trialing a Voice over IP (VoIP) service, called O2 Connect, which allows iPhone and Android handsets to make calls to mobile phones as well as landlines for free.

Currently available only to a small number of the invite-only customers, the new VoIP service requires the downloading of the Connect application and a WiFi hotspot.

The beta service involves just around one thousand O2 consumers and enterprise customers.

The service provider said that the service could eventually be made available even to customers of the rival networks.

Speaking on the topic, an O2 spokesperson said, “It’s potentially a great way for us to get ourselves and our brand in front of people who aren’t necessarily our customers.

The Connect app would also be made available on more platforms if the trial produced the desired results.

O2 Connect, which will challenge services like Skype and Google Voice, is an invention of parent company Telefonica’s O2 Labs and the recently opened Digital department.