What does data-only mean?

The plan provides internet only: no local number, no voice calls or SMS on that line. App calling — LINE, WhatsApp, FaceTime — works normally, and you can still receive SMS on your home number if that line stays enabled.

The term 'data-only' means a plan that provides internet connectivity through the eSIM line alone: no local phone number is attached to that line, and the line cannot make calls, receive calls, or receive traditional SMS at all. This page sets out plainly what works, what does not, and how to configure the phone if you need to rely on both your home line and the eSIM line at the same time while travelling.

It suits anyone about to buy a plan for the first time and wondering whether they can still call family or receive an OTP code, anyone who has used a local physical SIM with a number before and is unsure how an eSIM differs, and anyone planning which line should stay on for which purpose during the trip. This does not state the price or specifics of any one plan, since those vary by plan and supplier — check that plan's own page directly.

What data-only genuinely gives you

A data-only plan provides internet connectivity over the mobile network at your destination, enough for maps, chat apps, browsing, booking accommodation, and ordinary social media use. The speed and data allowance you actually get depend on the specific plan chosen and the network available in that area, not a fixed figure that applies across every plan.

What data-only does not provide is a local phone number that others can call, and there is no traditional call, receive-call, or SMS service over the mobile network on that line at all, whether that would be a long-distance call or a call made within the destination country itself.

Why most travel plans are built as data-only

Most traveller-focused eSIM plans are designed around internet access as the core need, since most travellers already lean on apps for communication rather than traditional mobile-network calls. Not carrying a local number also keeps the purchase and installation process quicker and simpler than having to register a brand-new number.

Some suppliers do offer plans that include voice and SMS in certain countries, but not every plan and not every country carries this. Check the Voice/SMS line on the plan page before buying, every time this matters to you.

App-based calling still works as normal

Calling through apps such as LINE, WhatsApp, FaceTime, or other video-calling apps does not use the traditional phone network at all — it runs over the internet connection instead. So as long as the eSIM line has usable data, calling through these apps works normally for both voice and video.

What needs checking is that the person on the other end also has the same app installed and is connected to the internet, since app-based calling requires both sides to be set up, not just yours.

iMessage, RCS, and other messaging that is not traditional SMS

iMessage on iPhone and RCS on Android are messaging systems that run mainly over the internet, not traditional SMS that depends directly on the mobile network. So as long as your eSIM line has usable data, sending and receiving messages through either system with another iPhone user, or an Android user who also has RCS switched on, usually continues to work as normal.

The catch is that if the other person is not using iMessage, or does not have RCS switched on, the message automatically falls back to traditional SMS, which cannot be sent from a data-only eSIM line at all, since that line has no traditional SMS capability whatsoever. Some phones simply show a failed-to-send message without explaining the real reason, which can be mistaken for a data or profile problem instead.

Business trips and using one line for both data and a contact number

For a business trip where clients or partners need a number to call back while you are abroad, a data-only line by itself is usually not enough, since there is no number for anyone to call back at all. The more sensible approach is to keep the original Thai number for contact, and let contacts know in advance which app you will mainly be reachable on during the trip.

If a genuine local number is needed for business reasons — coordinating with a local supplier, say — check in advance whether a plan including Voice/SMS exists for that country, rather than assuming an ordinary data-only plan will cover this need.

If you are deciding between data-only and a plan that includes Voice/SMS

The most direct question to help decide is whether anyone during this trip genuinely needs to call you directly through a phone number, rather than through an app. If the answer is no one at all, a data-only plan usually covers everything and tends to offer more options to compare. If the answer is yes, check whether a Voice/SMS plan actually exists for that destination country before buying anything.

If it is unclear whether an incoming-call number will be needed during the trip at all, choosing data-only first and keeping the original Thai number as a fallback for incoming calls is usually the safer choice, since changing your mind afterwards is far easier than trying to source a fresh Voice/SMS plan mid-trip.

You can still receive SMS on your Thai number, if that line stays enabled

If your home line — whether a physical SIM or another eSIM carrying your Thai number — stays enabled on the same phone alongside the travel eSIM, you can still receive SMS on that Thai number as normal, as long as the line stays switched on and has signal. There is no need to disable the original line just to use the new eSIM.

The cost and terms of receiving SMS while roaming depend on your original Thai carrier itself, not something the travel eSIM plan controls. Check directly with your original carrier if you are unsure about that cost.

Setting the phone up so both lines coexist correctly

1. 1Label each line so they are easy to tell apartGive the travel eSIM and the home line clearly different labels, such as 'Travel Data' and 'Thai Line', so later settings are not confusing.
2. 2Set the eSIM as the line that carries dataSet the eSIM line as the one that carries mobile data by default, and switch on data roaming for that line as well.
3. 3Keep the home line active for SMS and its own numberDo not disable or remove the home line if you still need to receive SMS or calls on your original number.
4. 4Check which line the apps you need actually rely onInternet-calling apps like LINE or WhatsApp will use whichever line has active data — there is no separate setting needed just for those apps.
5. 5Test both sides before travelling, if possibleTry receiving a test SMS and connecting to the internet on both lines before departure, to confirm everything is set up correctly.

Data-only does not mean 'internet calling is unavailable'

Many people mistakenly assume data-only means calling anyone at all is impossible, when in fact app-based calling still works exactly as normal. What data-only restricts is only the traditional call over the mobile network — the older method that dials a phone number directly, not calling over the internet.

If you are already used to relying mainly on app-based calling in everyday life, a data-only plan usually covers everything you need without feeling like anything is missing during the trip.

If you genuinely need a local number that can receive calls

If you genuinely need a local number that can receive calls — for example, to coordinate with a food delivery rider or a service that calls you back directly — check before buying whether that plan includes a Voice/SMS option. Not every supplier and not every country offers this.

If you are not sure whether the plan you are looking at includes this, check the help page on 'which plans include calls and SMS' or contact the team to confirm before buying.

Voice over apps in areas where data is not steady

App-based calling needs a reasonably steady data connection throughout the conversation. In an area with weak or intermittent signal, an app call can stutter, drop audio, or disconnect mid-conversation — unlike a traditional mobile-network call, which in many cases tolerates weak signal better, since it was built specifically for voice.

If an important work call or urgent conversation is expected in an area with unreliable signal — rural areas or buildings where signal struggles to reach, say — it is worth planning a backup, such as finding a spot with steadier Wi-Fi, rather than relying purely on mobile data for a call that matters.

How a local physical SIM with a number differs from a data-only eSIM

A traditional local SIM bought from a shop abroad usually comes with a local phone number and Voice/SMS support as a natural part of the product, whereas most travel eSIMs are built around data as the main focus, as explained above. This difference does not mean one is inherently better than the other — it depends on what your particular trip actually needs.

The advantage of a data-only eSIM is that it can be installed immediately before departure without hunting for a shop or waiting in line, whereas a physical SIM has to be bought and swapped in at the destination. If installation convenience matters more than having a callable number, a data-only eSIM usually serves better.

What works and does not work on a data-only line

Common mistakes

A common mistake is disabling or removing the original home line right after eSIM installation, assuming it is no longer needed, when in fact the original line is still needed to receive SMS and calls on your original number throughout the trip.

Another common mistake is expecting a data-only eSIM line to carry a number others can call back, when the plan page never stated it included Voice/SMS. Always check that line before buying if this matters to you.

Check this before you buy

• Read the Voice/SMS line on the plan page clearly before buying
• Decide in advance whether to keep the original line on for SMS alongside the eSIM
• Confirm the phone supports dual SIM or dual eSIM if two lines need running at once
• Have an internet-calling app both sides already use ready in advance
• If a bank OTP is expected, plan to keep the original line on — never rely on a data-only line for that

See the full eSIM installation guide