Russell discovers a very interesting new services that allows you to use a new application for mobile phones in the UK called BT Callwise. Apparently the Symbian software uses the data network to get your voice to their gateway (I'm still not 100% sure how it works):

"BT Callwise is a BT service which enables customers to make International calls from their mobiles at value for money prices. A piece of software is loaded onto your mobile handset which enables you to make calls over BT's network rather than the mobile provider's network. Differences between BT's and Mobile providers prices vary between countries. The new software on your mobile will add a new icon to the menu on your mobile phone. "

if this tech could be applied to more national networks it would be a revolution for the mobile market. Wow.