Three international roaming: how it works, what to check, and when a travel eSIM wins
Key facts
- Three international roaming is usually billed per day of use or bundled with a daily data allowance, with reduced speeds after the cap — check the current rate in the Three app before you fly.
- Roaming often has to be enabled before departure; confirm the destination is covered by your specific plan, not a generic list.
- VoaSim charges one price per duration for every destination: USD 23.90 for 7 days, USD 30.90 for 10 days, USD 42.90 for 15 days, with truly unlimited data.
- Your Three SIM and UK number stay in the phone; just turn off your carrier's data roaming so nothing bills twice.
- Carrier roaming still wins for one- or two-day trips with light use or destinations already included in your plan.
See the exact price for your dates
You are a Three customer, your trip is booked, and you want to know if your phone will just work when you land. Sometimes it does. Sometimes roaming is not switched on, or the country is not in your plan, or you burn the daily allowance on day one and spend the rest of the week on throttled speed.
This page explains the carrier roaming model in plain English, gives you a pre-flight checklist, and shows exactly when a travel eSIM is the cheaper, simpler call.
How carrier roaming is billed (the model, not the rates)
Rates change by country, plan and date, so check them inside the Three app or on Three's official site. What does not change is the model. Carrier international roaming generally works one of three ways:
- Bundled into your plan. Certain destinations are included at no extra charge, with a daily or monthly data allowance taken from your UK bundle.
- Per day of use. You are charged a flat fee only on days you actually use data, calls or texts abroad.
- Pay as you go rates. If the country is not covered, you pay standard out-of-bundle rates, which are the expensive option.
Two details catch people out. First, most carriers apply a fair use cap: once you pass it, speeds drop sharply or data stops. Second, roaming often has to be enabled before you travel, especially on newer or SIM-only plans. Check both in the app, not at the airport gate.
Pre-flight checklist if you stay with Three
Carrier roaming is perfectly fine for a lot of trips. If that is your plan, do these five things before you leave:
- Confirm the destination is covered by your specific plan, not by a generic list you saw online.
- Turn roaming on in your Three account and on the phone (Settings → Mobile Data → Data Roaming).
- Note the daily allowance and what happens after it — throttled speed or extra charges.
- Set a spend cap if your account allows it, so a stray app update does not surprise you.
- Download offline maps and boarding passes so day one works even if activation lags.
When is carrier roaming the better pick? Short hops of one or two days, light use (messaging, a few maps lookups), or plans where the destination is already included. In those cases nothing beats keeping your own number and doing nothing. See our roaming guides for more scenarios.
When a travel eSIM wins
An eSIM wins the moment your data use stops being light. Streaming on a train, uploading photos, hotspotting a laptop, video calls home, three weeks in one place — that is when daily allowances and throttling become the real cost.
A VoaSim travel eSIM is data only, with truly unlimited data: no cap, no throttling, no hidden fair use clause. It connects automatically to local networks on 4G and, where available, 5G, across 170 destinations. Your Three SIM and your UK number stay in the phone — WhatsApp keeps working on your number, you just turn off Three's data roaming so nothing bills twice.
The other advantage is predictability. One price per duration, identical for every destination. You know the number before you fly, and it does not change if you use 2 GB or 40 GB. Travelling around Europe? One eSIM covers 50 countries, including the UK, Switzerland, Turkey, Norway and Iceland.
VoaSim prices by trip length
Same price for every destination. Today's table includes the 15% promo:
| Duration | Price (USD) | Per day |
|---|---|---|
| 5 days | 18.90 | 3.78 |
| 7 days | 23.90 | 3.41 |
| 10 days | 30.90 | 3.09 |
| 15 days | 42.90 | 2.86 |
| 30 days | 61.90 | 2.06 |
| 60 days | 106.90 | 1.78 |
Trips of 1 to 4 days pay the 5-day package. Maximum 90 days per eSIM. A second eSIM in the same order gets 10% extra off, which is useful for couples. Payment is by international credit or debit card in USD through Stripe, with an invoice by email and no hidden fees. Run your dates through the price simulator to see the exact total.
Will your phone take an eSIM?
Dial *#06#. If an EID number appears, your phone supports eSIM. As a rule of thumb: iPhone XR or newer, Samsung Galaxy S20 or newer, Google Pixel 3 or newer, and most phones released from 2020 onwards. If your handset is still locked to a carrier, get it unlocked first — VoaSim does not sell physical SIM cards.
Delivery is by email within minutes: a QR code plus a step-by-step install guide for iPhone and Android. Install before you fly, then leave the eSIM line switched off until you land. Your days start counting at the first connection to a network at the destination, not at purchase. On Android, be careful not to enable the eSIM's data early.
If anything goes wrong, the free eSIM Rescue tool diagnoses an eSIM of any brand with no signal, and human support answers at hola@voasim.com. If the eSIM will not connect and support cannot fix it, you get a 100% refund.
Other options worth knowing
Being fair: VoaSim is not always the answer. Here is the honest landscape.
- Three roaming — best for one- or two-day trips, light use, or destinations already included in your plan. Zero setup.
- eSIMs sold by GB — Airalo, Nomad, Saily, Ubigi, Maya Mobile, GigSky and others sell local, regional or global data packages through their apps. Good if you genuinely use little data and want to pay for a small bundle. Check the cap, the validity window and the tethering rules in each one's terms.
- Holafly — sells unlimited-style plans with usage conditions described in its terms. Read them for tethering limits.
- Local physical SIM — cheap in some countries, but it means a shop, passport registration, airport time, and taking your UK number out of the phone.
Compare the shortlists on our comparison pages before you decide.
Why trust VoaSim?
Registered company with an invoice on every purchase, USD payment via Stripe with no hidden fees, human support and a guarantee: if the eSIM will not connect and support cannot fix it, you get 100% back.