After a long and tiring trip, I finally arrive at the Frankfurt Airport. I work my way to the regional train station, and in the few minutes before the train comes I decide to give my wife a call. I pull a few coins out of my pocket and drop on into the phone. I had nothing better to do then to chat while I waited for my train, so I proceeded to talk until the phone wanted more money. Feeling exceptionally stingy, I said goodbye and was promptly disconnected. Now comes the fun part. I hang up the phone, and it cranks out 14 times the amount of money that I spent on the phonecall!!!
I'm being intentionally vague in explaining exactly what I did, just in case it is reproduceable. I'll try the exact same procedure next time I see one of those phones... even if it was just a fluke of 'nature', hearing the sound of those shiny new euro cent coins clunking out of the phone made my day!