The pain of unexpected phone bills seems to have happened to everyone. Whether it be your kid texting too much, or roaming charges from a cruise ship, the mobile companies always have their ways of getting more of your money.
I went to London with my school when I was in high school. Of course my parents were scared to death of letting me go across the pond without them. I had my phone, it would work over there, it seemed great. Then I arrived in my hotel room, plugged it in to charge and fried my charger. Thanks a lot UK electricity! Well my phone died and I didn't have my annoying parents calling me all the time while I was on vacation, it was great. They freaked a bit, but I let them know every few days I was ok.
This infographic says that the VoIP service Skype is the cheapest option for communication between countries. With free video chatting to other computers it can't be beat, but if you want a mobile solution check out some other ways for [avoiding a large phone bill when traveling].