Picture yourself landing in Lisbon with plans to lean on your phone. Point the camera at a menu and get it translated. Ask an assistant which tram goes to the hotel. Let the AI-powered transit app reroute you round the strike nobody warned you about.
Then the arrival hall Wi-Fi asks for a passport number and a phone number you can’t receive texts on. The phone that was meant to be a genius tour guide is now a very expensive clock.
Travel phones have changed. The AI features that make them useful abroad mostly assume you’re online. So choosing how you connect is no longer a dull admin task before a trip. It decides how much of that AI toolkit you can actually use.
Fonus, one of the providers covered here, puts a big claim in its homepage title: “Discover the best international eSIM – Fonus”. Whether it’s the best depends a lot on how you travel. Here’s how to work that out.
Which AI features work offline, and which don’t?
It’s less clear-cut than you might expect.
Some AI now runs on the phone itself. Apple’s Live Translation, introduced with iOS 26 for conversations through AirPods, processes speech on the device. Google Translate lets you download language packs for offline text translation. Both hold up surprisingly well with no signal, and AI translation keeps closing the gap with human quality, which makes these features more trustworthy each year.
Plenty doesn’t. Phone makers increasingly run a hybrid: Samsung’s Galaxy AI, for example, keeps some tasks such as core call translation on the device and sends heavier generative jobs to the cloud, so Galaxy AI and ChatGPT behave very differently once your signal drops. General assistants like ChatGPT and Gemini need a connection, and voice mode can chew through data faster than people realise. Camera-based visual search usually needs the cloud, and so do AI trip planners, live transit rerouting and review summaries. So does almost anything that has to know what’s happening right now, such as a closed station, a sold-out museum or a cancelled train.
In practice, the useful stuff, real-time help with real-world problems, is the part that needs data. Plan for that.
Why roaming still stings
The old default was to leave your home plan running and pay the carrier’s daily fee. US carriers’ international day passes typically cost around $10 to $12 a day. You keep your number and get data, and the charge adds up even on a day you barely touch the phone.
Over a 10-day trip that’s roughly $100 to $120. That’s fine for a quick business hop, but painful for anything longer.
Travel eSIMs are the alternative, and they’ve gone mainstream. Analysts at CCS Insight estimated about 134 million travel eSIMs in use in 2026, up from roughly 102 million the year before. Hardware has helped. US iPhones have been eSIM-only since the iPhone 14, and Apple’s iPhone Air dropped the physical SIM tray everywhere. For a growing number of travellers, the question isn’t whether to use an eSIM but which one.
What to check before you buy anything
Price is the easy part. What decides whether the phone still works on day two is everything else.
Is your phone unlocked? A carrier-locked phone won’t accept another provider’s profile. Check before you leave, because sorting it out from abroad is miserable.
Is your next stop actually covered? “100+ countries” helps only if Thursday’s destination is on the list. Read the full country table, not the globe icon.
What does “unlimited” really mean? Usually it’s fast for a set number of gigabytes, then slow. Find that number. For heavy AI use, especially voice assistants and video calls, it matters a lot.
Data only, or calls and texts too? Most travel eSIMs are data-only. That’s fine for WhatsApp, but no help if clients call your number or your bank texts a login code. A VoIP number (calls over the internet) helps, but it won’t always receive bank verification texts. Banks are fussy about VoIP.
Can you share the connection? Hotspotting to a laptop is handy on trains. Some plans restrict it.
When should you install? Download the profile on home Wi-Fi before you travel, then switch it on when you land.
A quick sense of scale
Say a 10-day trip through two countries involves maps, email, a few video calls, regular AI assistant use and some hotspotting on trains. That typically comes to somewhere between 5 GB and 15 GB.
The day-pass route costs around $100 to $120 and keeps your number. Two single-country data packs in Europe can cost a fraction of that, but you’ll lose ordinary calling on the travel line and have to buy again at every border. A monthly multi-country plan starts to make sense once you’re crossing borders regularly, or if you’ll be travelling again within the month.
The options, by type of traveller
Prices on these services change constantly, so treat this as a guide to fit rather than a price list. Check current plans before buying.
For frequent border-crossers who need a real phone line: Fonus Mobile
Fonus is built differently from most of the field. It’s a monthly subscription, not a trip pack. Its World Unlimited plans cost $19.99 (Starter), $29.99 (Plus) and $49.99 (Max) a month, and all three include data, calls and texts across more than 100 countries with no roaming fees.
High-speed data runs to 5 GB on Starter and 20 GB on Plus, then drops to 3G-equivalent speeds. That’s fine for messages and maps, less so for video or chatty voice assistants. Max has no fixed cap, though Fonus notes speeds can still slow with excessive use or on busy networks.
Calls and texts go through the Fonus app over VoIP, and you can set the app as your default dialler. It also offers local numbers in 14 countries, including the US, UK, Canada, Australia, Mexico and several European countries, and you can keep more than one number on the same account.
Best for: digital nomads, remote workers and anyone who needs a reachable number across several countries every month. Watch for: the high-speed caps on lower tiers, and the usual VoIP limits with bank verification texts.
For short, planned trips: Airalo
Probably the best-known name, with country, regional and global data packs and one of the widest destination lists around. Setup is simple: pick, pay, scan. It’s mostly data-only, so calls still depend on your home SIM or messaging apps.
Best for: one trip, a known itinerary, no fuss.
For heavy data users on a holiday: Holafly
Unlimited data plans sold by the day or by blocks of days, aimed at people who don’t want to watch a gigabyte counter. Fair-use rules and hotspot limits still apply, and the longer plans aren’t cheap.
Best for: a week or two of heavy phone use with an unpredictable data appetite.
For the privacy-minded: Saily
From the team behind Nord Security, with web-protection features bundled alongside the data. The country list is narrower than the biggest catalogues.
Best for: travellers who already want a VPN-style layer and would like it in the same app.
Also worth a look
Ubigi offers a broad catalogue and 5G where partner networks support it. Nomad is popular as a budget option. HelloRoam names the host networks on many country plans, which helps if you’ve been stuck on a weak partner network before. aloSIM lets you choose how long a small plan lasts. Jetpac focuses on longer validity with travel extras. SimLocal’s Orange Holiday World offers a single global profile for a trip of about a month.
Almost all of these are data-first. None replaces a monthly phone line with kept local numbers, which is the gap Fonus is going after.
So which is “best”?
It depends on the trip.
For a long weekend in one country, a small data pack wins on price. For two weeks of heavy streaming and constant AI-assistant use, an unlimited holiday plan makes sense. For a 48-hour business trip where your number must keep working, the carrier day pass is still the easiest option.
If you live across borders, though, regularly working from different countries and needing people to reach you on a real number while your phone does its AI tricks over data, a monthly global line like Fonus starts to make a lot of sense.
Whatever you choose, download the profile before you fly. Your translation app will thank you in the arrival hall.
Related: AI Travel Assistants Need Internet: Why Your eSIM Matters
