Install the eSIM the night before you leave, not at the airport

It seems sensible to leave the eSIM until you are nearly there. The trip has not started, so why start the plan. And there is always a spare half hour at the airport.

In practice the half hour disappears into queues and toilet trips, and the airport wifi wants a form filled in before it loads anything. Installing an eSIM means downloading a profile over the internet. Doing that on a weak connection, with a tired child and a boarding call, is how a simple job becomes a problem you carry onto the plane.

What you need at home

Three things. The phone, charged and connected to your home wifi. The SIM details from the PERDIEM console: the QR code, the activation code and the ICCID. And, if you plan to scan the QR code, a second screen to show it on, such as a laptop or another phone. A phone cannot easily scan a code shown on its own screen.

PERDIEM does not email SIMs, so the details are wherever you choose to put them. If you are setting up someone else's phone, share them privately, or simply do the install yourself.

If there is no second screen to hand, most phones also let you add an eSIM by typing the details in. Look for an option to enter them manually, and use the activation code instead of the QR code.

Installing it

On an iPhone, the option is in the mobile data section of Settings, usually called Add eSIM. On Android, look in the network or connections settings for a SIM manager or an option to add an eSIM. The exact names vary between versions and manufacturers, so follow whatever wording your phone uses.

Scan the code or enter it. The phone downloads the profile, which usually takes a minute or two. When it asks what to call the new line, choose a name you will recognise later, such as Travel. Leave the home line as it is.

Then make sure the travel line is not set for mobile data yet. The profile sits on the phone, ready for when you arrive.

Will the plan start early?

It depends on the plan. Many travel data plans start when the phone first connects to a supported network in the destination. Some start when the profile is installed. Read the terms of the plan when you pick it, and if they are not clear, allow a day's margin rather than assuming.

If a plan would start on installation and the trip is short, install it on the morning you leave, while you are still at home on your own wifi. You keep the benefit of not doing it at the airport.

When you land

Once you are off the plane, switch the travel line on and set it as the line for mobile data. Most travel eSIMs need data roaming turned on for that line, because the local network is not the provider's own. That is normal, and it does not mean your home network is charging you.

On the home line, do the opposite and turn data roaming off. The home line can stay on for calls and texts, but it should not be using data abroad. On an iPhone, also check that the setting allowing mobile data to switch between lines is off, so the phone does not drift back to the home line.

Give the phone a minute or two to find a network. If nothing connects, restart it once before trying anything else.

Do not delete it

If something looks wrong, resist the urge to delete the eSIM and start again. With many providers an eSIM can only be installed once, and a deleted one may not come back from the same code. Check the settings above, restart the phone, and only then look for further help.

Keep the SIM details in the console until everyone is home. The ICCID is the number any support conversation will start with.