eSIM basics
What is an eSIM?
Every phone needs a SIM to prove to a network who you are. For thirty years that was a removable card. Since about 2018 most phones have carried a small reprogrammable chip that does the same job, and an eSIM profile is simply the credentials written onto it.
For a traveller the practical differences are these. You can buy data for another country before you leave home, and it works the second you land. You do not have to find a shop at the airport, hand over your passport, or keep a fiddly tray tool in your bag. Your normal number stays active on your normal line at the same time, so you still get your calls and your messages.
The part nobody says out loud is that most travel eSIMs are data only. They carry no phone number, which is why your bank code never arrives. That is a product decision rather than a limit of the technology, and it is one we fixed.
eSIM against a physical SIM
| Travel eSIM | Local SIM at the airport | Roaming on your home plan | |
|---|---|---|---|
| Set up before you fly | Yes | No | Yes |
| Keep your own number | Yes | No | Yes |
| Typical cost for 5 GB | $9 to $17 | $5 to $25 plus a queue | $50 and upwards |
| Needs a passport and paperwork | No | Often | No |
| Works the moment you land | Yes | After you find the shop | Yes |
8
eSIM profiles a recent iPhone stores
5
Profiles many Android handsets stop at
60 percent
Of no service reports are the roaming toggle
60 seconds
Automatic refund if provisioning fails
What is actually inside the phone
The chip is called an eUICC and it is soldered to the board. It carries its own serial number, the EID, which is how a network sends a profile to your handset rather than to somebody else's.
You can check yours in ten seconds. Open the keypad and dial star hash zero six hash. If an EID appears alongside the IMEI, that phone has an eSIM. On an iPhone the same row is in Settings, General, About. On Android it is usually in Settings, About phone, Status.
No EID means no eSIM, whatever a compatibility list on the internet says. Model names get reused across regions, and a phone sold in one country can lack the chip its twin has in another. The device is the only source worth trusting.
Carrier locking, the one thing that can stop you
A handset bought on a contract can be locked, and a locked phone can refuse a third party eSIM even when the chip is there and the EID shows up. That is a carrier policy rather than a hardware limit, and nothing you install will change it.
Ask your carrier to unlock the device. It is usually free once the contract is paid off and it can take a few days, so do it before the trip rather than at the airport. A few countries also restrict third party profiles outright, and where that is true we say so on the country page instead of taking your money.
If provisioning does fail, the charge comes back automatically inside 60 seconds. No ticket, no form and no conversation.
Dual SIM, on iPhone and on Android
Dual SIM is two different things that get confused. How many profiles a phone can store, and how many lines it can run at once. Almost every eSIM capable phone runs two lines at once. Storage is where the platforms differ.
A recent iPhone stores around 8 profiles and keeps 2 of them active. You set one line as Default Voice and point Cellular Data at the other. Then turn off Allow Cellular Data Switching, in Settings, Cellular, Cellular Data, because that setting is the mechanism behind most surprise roaming bills.
Android runs two lines too, but several popular handsets store only 1 to 5 profiles, and a few older models overwrite the one already there. The settings path also differs on Samsung, Pixel, Xiaomi, OnePlus and Motorola, which is 5 different routes to the same screen.
The failure people actually hit is neither. Around 60 percent of every no service report we receive is a travel line with data roaming switched off, on a phone that is otherwise working perfectly.
Why a travel eSIM has no phone number
A mobile subscription has two separate parts. The identity, the IMSI, which the network checks to let you on. And the number, the MSISDN, which a text message is addressed to. You can have the first without the second.
Travel eSIM providers buy data only subscriptions because they are cheaper and easier to move across borders. A data only profile has an IMSI and no MSISDN, so the network authenticates you and gives you internet, and your bank hands its code to a gateway addressed to nobody. The code is not late. It was never deliverable.
There are three fixes and two of them are free. Keep your home line switched on for texts, with its own data roaming off. Turn on wifi calling before you leave, because most carriers will not let you enable it once you are abroad. Or add an Orbislo Number, which is a real mobile number rather than a VoIP range that banks reject on sight.
What happens to your normal SIM
Nothing. It stays where it is, physical or eSIM, and it keeps your number, your contacts and your two factor codes. Adding a travel eSIM is not switching carrier.
Three settings matter and one of them reads backwards. Data roaming off on your home line, because that is the one that costs money. Data roaming on for the travel eSIM, because a foreign issued profile is always roaming from the phone's point of view, so switching it off simply stops it working. And mobile data pointed at the travel line while calls stay on the home one.
When you fly home, nothing happens either. Your home line takes over, the travel line goes quiet, and with Orbislo whatever data you did not use is still in your wallet.