There are times of course when I cannot punish idiots. On occasion an idiot may punish himself - and not even know it. It's not as good as actually dishing out the punishment, but sometimes you settle for second best.
Case in question? Sure. Person calls a mobile phone from overseas weekly for about 5 min and runs up their bill, disregarding the alternative of calling a landline number at the same timeslot. The cost to call the mobile is about 5 times that of calling the landline.
Now someone must be thinking, why not give them the landline number. Oh yes - they have both numbers but opt for the mobile for no obvious reason. Now you might be thinking there is some advantage for them to calling the mobile that I'm not seeing. No. No such advantage.
Now you might be thinking that the person doesn't know that calling a mobile in that country is far more expensive than to a landline. No. That one has been ruled out as well.
Conclusion supported: Human stupidity is based on - just that - the absence of a logic, or the absence of an intelligence acting on a logic.