[MacWilder]

Good thinking. International GSM data is incredibly expensive. Mere average use will run up 100's of Euros charges. There are ways to turn it off but it depends on the ROM one is using. Even then, there can be a problem of data continuing to work. I suggest that, rather, you contact your provider and tell it to turn off international data (as it can). Then, if something goes wrong, it's the providers fault and you won't be charged.