As I like to try and save you pennies on your mobile calls I thought I'd let you know about this little gizmo: Gizmo VoIP. It's a Skype-style piece of software that means expensive mobile calls should be a thing of the past. Gizmo works by connecting all your calls to the Internet not the mobile network. Simple. And it's easy to install and set-up
All calls from a Gizmo user to another Gizmo user are completely free, so if you use the service and like it, it might be worth trying to convince all your friends and family to get it too. Land and mobile rates from Gizmo to non-Gizmoers(?) are cheaper than normal. Check the website for full details. Plus there are lots of additional features that are quite nice, including multi-network chats with MSN friends, conference calling, and Meta-Voice which allows you to call friends on Yahoo Messenger, MSN and Google Talk for free. Also if you participate in the All Calls Free plan you can get a number of free minutes each month for mobiles and landlines. Some of these add-ons though felt a bit invasive to me, as though they wouldn't let me rest until I signed up for something that cost me money.
Alternative Skype-style cheap call provider, but do you want to change provider?