Calling abroad: roaming, local SIMs, eSIMs, Wi-Fi calling and apps compared
There is no single cheapest way to call when you travel. The right choice depends on where you go, who you need to reach, whether people need to reach you on your usual number, and how much data you have.
First, get the number format right
Whatever method you use, store contacts in international format: a plus sign, the country code, then the national number without its leading zero. A Brussels number written 02 xxx xx xx at home becomes +32 2 xxx xx xx. This is the E.164 format defined by the ITU (Recommendation E.164), which limits international numbers to 15 digits. The "+" tells the phone to use whatever international prefix the local network needs (00 in most of Europe, 011 from North America), so the same contact works in every country and in calling apps.
Option 1: roaming with your own SIM
Best for: trips inside the EU/EEA, or short trips elsewhere when your operator has a reasonable day pass.
Inside the EU and EEA, roaming is usually included at domestic prices (see EU roaming rules). Outside that zone, prices are set freely by each operator and range from affordable daily passes to steep per-megabyte charges. Your number keeps working, which matters for banking codes sent by SMS and for anyone who needs to reach you.
Catch: check the per-day and per-megabyte price for your destination before leaving, and be wary of ships, planes and border areas.
Option 2: a local SIM card
Best for: longer stays, heavy data use, or calling many local numbers.
Buying a prepaid SIM from a local operator gives you local rates and a local number. Many countries require identity registration for SIM cards, often with a passport, so allow time at the shop or airport kiosk. Your phone must be unlocked to accept another operator's SIM.
Catch: your usual number is unreachable unless your phone supports two SIMs at once (a physical SIM plus an eSIM is common), in which case you can keep your home line for SMS and calls while using the local SIM for data.
Option 3: a travel eSIM
Best for: data on short trips, set up before you leave.
An eSIM profile can be bought online and installed by scanning a QR code or through an app, with no shop visit. Many travel eSIMs are data-only: they give you internet access but no local phone number, so calls go through apps or Wi-Fi calling on your home line. Our eSIM guide explains compatibility, carrier locks and dual-SIM use.
Catch: your phone must support eSIM and must not be locked to a single operator, and coverage depends on which local network the eSIM provider uses.
Option 4: Wi-Fi calling on your home number
Best for: calling home from hotels and rentals with decent Wi-Fi, when your operator charges such calls as domestic.
With Wi-Fi calling enabled, your phone connects to your home operator over the internet. Many operators treat calls from abroad back to your home country as domestic calls; calls to local numbers in the country you are visiting may be charged as international. Some operators restrict Wi-Fi calling in certain countries.
Catch: rules are set by each operator; read the tariff page, and remember that switching to a local SIM for data does not prevent you from using Wi-Fi calling on your home line on a dual-SIM phone.
Option 5: app-to-app calls
Best for: family and friends who use the same app.
WhatsApp, Signal, FaceTime and similar apps call other users over any data connection at no extra cost beyond data, often with better audio than a phone call and with end-to-end encryption (see what calling apps encrypt). A voice call uses modest amounts of data; our data usage guide shows the calculation.
Catch: both sides need the app and a working connection, these apps generally cannot call emergency numbers, and some countries restrict or block particular calling apps, so have a fallback.
Option 6: VoIP-to-phone credit
Best for: calling landlines, businesses and people without smartphones in another country.
Several services let you buy credit and place calls from an app to ordinary phone numbers worldwide, connecting your internet call to the telephone network through a gateway. This is how the smartphone calling services of the early 2010s worked, and it remains useful for calling a hotel, an airline or a relative's landline. Rates differ widely between destinations and between calls to fixed and mobile numbers.
Catch: the person you call may see an unfamiliar or withheld caller ID unless the service lets you verify and display your own number (see caller ID and keeping your number), and these services are not a substitute for emergency calls.
Summary table
| Method | Keeps your number | Reaches any phone | Typical cost driver |
|---|---|---|---|
| Roaming | Yes | Yes | Operator's roaming tariff (domestic prices in EU/EEA) |
| Local SIM | Only with dual SIM | Yes | Local prepaid prices |
| Travel eSIM (data) | Only with dual SIM | Via apps or Wi-Fi calling | Data package price |
| Wi-Fi calling | Yes | Yes | Home tariff, operator rules for abroad |
| App-to-app | App identity | No, same app only | Data only |
| VoIP-to-phone credit | Depends on service | Yes | Per-minute rate by destination |
A sensible default
For most trips outside the EU, a combination works best: keep your home SIM active for SMS codes and incoming calls (with data roaming off if it is expensive), add a local or travel eSIM for data, and use app calls or Wi-Fi calling for the conversations themselves. Note the local emergency number before you go; 112 works across the EU and is recognised by many phones elsewhere, but not by every network worldwide.