How to use your phone abroad without getting a bill that makes you rethink your life choices

A friend of mine came back from two weeks in Japan and found a $400 roaming charge on her phone bill.

She had turned on international roaming because her carrier told her “it’s only $10 a day.” She had also, it turned out, not turned it off before she boarded her connection home and had a three-hour Tokyo layover on the way back. The $10-a-day plan had a daily cap. The layover was technically a new day.

This is entirely a setup problem, not a Japan problem.

Using your phone internationally is completely fine and costs almost nothing if you set it up correctly. Here’s how.

The three options: roaming, local SIM, eSIM

International roaming through your home carrier means your phone uses mobile networks in the country you’re visiting and you’re billed by your home carrier. This is the default if you do nothing. The cost varies enormously:

Some carriers include free roaming in their plans (Telstra Roam Free in Australia for certain countries, T-Mobile US’s international plan, many European carriers for EU roaming)
Others charge daily rates ($5-15/day is common)
Others charge per megabyte with no cap, which is where the horror stories come from

The critical thing to check: roaming charges in countries NOT covered by your plan’s roaming zones. US carriers often have good North American and European roaming but poor Asia-Pacific coverage. Australian carriers have good Pacific coverage but patchy Southeast Asia rates. Read the fine print for your specific destination, not just “international roaming: yes.”

A local SIM means buying a physical SIM card at your destination, swapping it into your phone, and using a local data plan. Usually much cheaper than roaming. The drawbacks: your home number doesn’t work (texts and calls to your normal number go unanswered), you need an unlocked phone, and you need to find a SIM shop when you arrive, which in some airports is easy and some isn’t.

An eSIM is a digital SIM that installs on your phone without physical swapping. You buy a plan online before you travel, download the eSIM profile to your phone, and it activates when you land. Your home SIM stays in the phone and keeps your number active for texts and calls (you can receive them over wifi). Best of both worlds: local data rates, your regular number still works.

eSIM: the full explanation

Your phone has a physical SIM tray (the one you put your carrier’s SIM in) and, in most phones from 2018 onwards, a built-in eSIM chip.

An eSIM works like a digital version of a physical SIM. Rather than inserting a card, you scan a QR code or tap a link and the plan installs directly. The phone can then use either the physical SIM or the eSIM, or in some configurations, both at once (dual SIM).

The practical setup: while you’re still home with a reliable wifi connection, you purchase a travel eSIM plan for your destination. Install it. Set your data to route through the eSIM when abroad. Land. Have data immediately, without the airport SIM hunt.

This is the setup I use for every country I visit. I’ve compared the specific eSIM options for most of the countries on this site. The difference in cost between a well-chosen travel eSIM and your carrier’s roaming rates is usually significant. India is a good example — it has specific regulations for foreign visitors that most generic advice gets wrong.

Does your phone support eSIM? Check Settings > About > look for eSIM or SIM information. Or Google your phone model and “eSIM support.” iPhones from XS onwards all support eSIM. Most flagship Android phones from 2019 onwards do. Some budget Android phones don’t.

Important: if you bought your phone from a carrier with a locked contract, it may be SIM-locked and not accept eSIMs from other providers. Check with your carrier if you’re unsure.

Before you leave home: the setup checklist

Turn off roaming. Unless you’ve confirmed your carrier’s roaming rate in your destination is acceptable to you, turn data roaming off before you board. Settings > Mobile/Cellular > Roaming > Off (on iPhone). Settings > Network > Mobile Networks > Data Roaming > Off (on Android, varies slightly by manufacturer). This prevents any accidental roaming charges if your eSIM connection glitches.

Download offline maps. Open Google Maps, find your destination, tap the three-dot menu, and select “Download offline map.” Select the area. Download it. Now Maps works fully without data. Do this for every city you’re visiting while you’re on wifi.

Download your translation language packs. Google Translate > tap the three-bar menu > Offline Translation > download the relevant languages. Korean, Japanese, Thai, Arabic, Hindi are the ones that matter most for non-Latin scripts.

Download your entertainment. Spotify playlists downloaded offline. Netflix episodes or films downloaded. Books on Kindle app. Long flights and transit journeys happen. Have something that works without connection.

Configure WhatsApp (or Signal) to call over wifi/data. This is how you call home for free. WhatsApp calls route over the internet rather than the phone network. When you’re on wifi at your accommodation, calling back home costs nothing. On data, it uses a modest amount but nothing significant.

Set up your banking app. Confirm your bank’s app works from abroad (some have geo-blocks), know your PIN, and have the fraud/emergency contact number saved somewhere offline. Also confirm whether your card works internationally, and whether you have a fee-free card. If you don’t have one, get one before you leave. Wise and Revolut are the most commonly used options.

How to structure your phone’s connectivity abroad

The setup I use (dual SIM: home carrier physical SIM + travel eSIM):

eSIM for data. Set the eSIM as the default data line. This routes all apps, maps, WhatsApp, and browsing through the local travel data plan.
Physical SIM on. Keeps my home number active to receive texts and calls, including two-factor authentication texts from banks. I don’t browse on it. No data roaming on the physical SIM.
Result: I can receive a bank verification SMS on my normal number, all apps run on the cheap local data plan, no roaming charges.

This works on dual-SIM capable phones. Most modern phones support this configuration. On iPhone: Settings > Cellular > set the eSIM as Default Line for cellular data, keep the physical SIM for calls/texts.

What changes by country

European Union. EU roaming rules mean that if you’re from an EU country, your EU carrier’s domestic plan works across all EU member states at no extra charge. If you’re visiting Europe FROM outside the EU, these rules don’t apply to you and a travel eSIM or local SIM is still the right call.

United States. US carriers tend to have decent coverage in Western Europe and Canada but variable Asia-Pacific coverage. T-Mobile includes basic international data (slow 2G, essentially useless for real use) in its plans with the option to pay for higher speed. AT&T and Verizon have daily international plans. For any trip of more than a few days in Asia, a travel eSIM is substantially cheaper than US carrier international rates.

Japan. Japan has excellent mobile coverage (4G/LTE everywhere cities exist, 5G expanding rapidly). eSIM options for Japan are excellent. Physical SIM options for tourists are also good (IC SIMs available at airports from multiple providers). Japan is a genuinely tech-friendly destination for phone setup and you have multiple good options.

India. Getting a local SIM in India as a foreigner used to require navigating a bureaucratic process that could take a day. eSIMs have made this much simpler. International visitors can now use travel eSIMs with full coverage across major carriers. Note: India requires phones to support LTE Band 3, 40, and 41 for best coverage. Most recent flagship phones do. Older budget phones may have limited connectivity in rural areas.

China. Foreign SIM cards and eSIMs from international providers work for connectivity in China. What they don’t solve is the Great Firewall: Google Maps, Gmail, WhatsApp, Instagram, and most Western apps are blocked within China regardless of what SIM you have. You need a VPN installed BEFORE you cross the border (VPN apps and websites are blocked in China, so downloading one after arrival isn’t possible). Install, test, and confirm it works before your flight.

Australia. Good 4G/5G coverage in major cities and along the east coast. Coverage gaps in the outback and remote areas are significant and well-known. For road trips outside metropolitan areas, a domestic SIM from Telstra has better rural coverage than other carriers. International visitors can get prepaid SIMs at airports.

Morocco. Good coverage in cities and on major routes. Rural areas and the Sahara region have variable coverage. Travel eSIMs work. Local SIMs from Maroc Telecom or Inwi are available at airports and shops, reasonably priced.

Apps that need data vs apps that work offline

Always need data:

Live Google Maps navigation (offline maps work for most directions but public transit directions need data)
Translation via camera (camera mode needs a connection for most scripts unless language pack is downloaded)
Booking apps
Banking apps
WhatsApp calls

Work offline (if you prepared in advance):

Google Maps offline map navigation
Google Translate with downloaded language packs
Spotify with downloaded playlists
Netflix with downloaded content
Kindle
Your banking app PIN entry (usually)
Documents saved to phone storage

The ratio you want: have your most-used apps working offline so low data is functional, and use data for the real-time things that need it.

The things that still trip people up

iMessage vs SMS. iMessage (the blue bubble) requires internet. Regular SMS (the green bubble) routes over the carrier network. If you’re using an eSIM for data and your home SIM has no roaming signal, iMessage to other Apple users still works over the eSIM data. SMS to non-iPhone users (or in areas with no carrier signal) routes over your carrier, which may be roaming. Know the difference and use WhatsApp for international messaging instead.

Tethering. If you’re using your phone as a hotspot for your laptop, that data comes out of your plan at a much faster rate than normal phone use. A 3GB plan that’s plenty for maps and WhatsApp can disappear in an afternoon of laptop work via hotspot. Get a plan with enough data if you’re working remotely.

Airplane mode on flights. Turn on airplane mode for the flight. Obvious. But: you can turn on wifi separately while in airplane mode on most flights with onboard wifi. Your cellular (including eSIM) stays off; the wifi connects.

Two-factor authentication abroad. If your home bank sends verification codes to your home number and you have no signal on that number, you can’t complete authentication. Test this before you travel and have backup authentication methods (auth app, email, backup codes) configured.

The whole thing is genuinely simpler than the horror stories make it sound. Buy the eSIM before you land, turn off roaming on your physical SIM, download your maps offline. That’s most of it.