I'd like to bring my iPhone on a cruise that will be outside the US part of the time. I've heard horror stories of people accruing thousands of dollars in charges without knowing it because their phone accessed the internet. Is "airplane mode" what I need to do? I know my phone is constantly going and looking for app upgrades, map locations, heck it even knows which Starbucks I'm in. Would appreciate some knowledgable help so I don't blow my Christmas budget on phone charges. Thx!