in the past, I have had problems with the other party getting charged for international texting rates for iPhone-to-iPhone iMessaging. I did not think this would be a issue. Could this be because one party had their phone # listed as one of the "reached at" or "start new conversations from" rather than just an email address? I am traveling soon, and I want the option to use iMessage without any complications or additional charges. Any insight is much appreciated. Thank you!