Not quite a mistake, but a misunderstanding. You do get unlimited Skype calls on 3, but only using their software which, rather than connecting over the internet, dials a number which then connects to the other Skype account. It uses a version of iSkoot; I understand that if you know the right settings you can get vanilla iSkoot to work. However, given the built-in Skype capabilities of the n900 I doubt iSkoot will be ported to Maemo.