Mobile providers
によるポスト 削除すみユーザー に フランクフルト フォーラム
You're right, I'd never thought that there will be offers for calls made from a mobile within Europe below 50 cent!
The only disadvantage is that these providers operate over internet only, so you can't get costumer service in a provider shop or something. But still, very handy.
By the way Martin, where did you find all these providers (blau, solomo)? If you don't know the name, there's no chance you'll find it by coincidence (at least I didn't...).