That is a great question. The last thing we want is for you to receive additional charges while traveling. Your Apple Watch will not work outside of the US. Having said that, we still recommend that you take steps to turn off the cellular data on the watch. You can use this link as a guide: https://www.verizonwireless.com/support/knowledge-base-215399/ Also, you can simply turn on Airplane Mode for the duration of the trip. Let's us know if this helps.