Get Your Phone Unlocked
Recent legislation has made this easier, especially if the phone is more than a year old. If your device is technologically compatible with a network in your destination ountry, unlock it and purchase a prepaid SIM from a local carrier when you land.
Buy a Data Package in Advance
Check to see if your carrier offers a deal for your destination. The majors post lists of supported countries online. Suss out your monthly usage and get the data package that meets your needs. They start at around $30 and include unlimited or very cheap texting.
Grab Some Apps to Help Manage Your Usage
If your international plan charges for texting, download WhatsApp or Line (stickers!) and use one of those instead. The app My Data Manager provides alarms to notify you about your data consumption and lets you limit mobile data usage via the device settings. It’s available on iOS and Android.
Minimize Background Data Transfers
Switch off automatic email downloads and background app refreshes. Also deactivate automatic syncing to services like iCloud, Google, and Dropbox. While abroad, only download and sync when you have access to Wi-Fi.
Neuter Your Less-Used Apps
Disable background data usage for any feature that isn’t critical. Allow only your most needed apps to access your precious data pipe. In iOS, go to Settings > Cellular and scroll down to your list of apps. In Android, go to Settings > Data Usage and scroll down.
Last Resort: Go Wi-Fi Only
If you can’t get an international plan for your destination, the safest option is to turn off data roaming entirely. In iOS, the toggle switch is under Settings > Cellular. In Android, it’s under Settings > Wireless & Networks > Data Usage. Phone calls and texts will come through, but data will only be sent and received when there’s Wi-Fi available.
How to Prep Your Phone for Travel Abroad | WIRED.