The mobile internet network operator Truphone has added a suite of advanced features to its beta VoIP service for mobile phones, and extended its offer of free calls to 40 countries until the end of 2007.

The SMS over IP capability brings the prospect of unlimited free SMS messages between on-net Truphone users, with a flat-rate tariff of 7p to all other regular mobile numbers worldwide.

The presence functionality enables users to know exactly when they can make a free call or send a free text message to another Truphone user while a smart log-on means a Truphone-enabled handset now automatically connects to previously used Wi-Fi access points.

Truphone over 3G has been made available at the request of customers with suitable 3G tariffs. While this allows low cost VoIP calls from many more locations, Truphone still recommends VoIP over Wi-Fi as being of higher call quality and less susceptible to high charges data charges.

Multi-SIM capability means Truphone supports travellers who take international SIM cards with them abroad. Calls to their Truphone number will reach them whichever SIM they're using at the time.

Truphone 3.0 also brings compatibility with a greater number of routers, reducing the likelihood of port-blocking; a simplified, more intuitive installation process; and a significant number of bug-fixes.

Existing Truphone customers and anyone signing up for Truphone before September 30th can make free Truphone calls to 40 countries until the end of 2007.

You can get Truphone by sending a text message with the word "Tru" to 07624 000000.

This is a simplified round-up of the services on offer, for small print and exclusions see the site for more details, link below.