Hello
HYEON WOO JEONG Welcome to the customers helps Vodafone's community.
That is a nice trip, it will have been a long bus ride. What the problem is that when you are in places where there is not enough, or good, range, your device makes a lot of contact with transmitter masts. Not using your device but having it on is already a use of the internet. Every time he searches and with every phone there are always sneaky apps that contact the internet every time. You do not have to have done anything yourself, but then data goes through.
In addition, it is difficult to say because you are abroad and it is always different than in the Netherlands. Maybe they use more data or other reasons why it goes so fast. If you make such a trip again, turn your roaming OFF and make sure you do not make internet connection with your device.
I hope to have informed you sufficiently. If you have any questions, please contact
Vodafone customer service.