Two lines, one phone: managing dual SIM while you travel

Why keep your home line on

Plenty of travellers still need their usual number abroad: banks send one-time codes by SMS, some messaging apps are tied to it, and family may call it. Most modern eSIM-capable phones support dual SIM, which lets you keep your home line for calls and texts while a travel eSIM handles data.

The risk is that your phone uses the wrong line for data and your home carrier bills roaming. A few settings prevent that.

The settings that matter

Names vary between iPhone and Android, but the ideas are the same:

• Mobile data line: choose the travel eSIM.
• Allow mobile data switching (iPhone) or automatic data switching (Android): turn this OFF so your phone doesn't fall back to your home line.
• Data roaming: ON for the travel eSIM, OFF for your home line.
• Default voice line: your home line, if you want to receive calls on your usual number.

Calls and texts on the home line

Check your home carrier's charges for receiving SMS, making or receiving calls, voicemail and Wi-Fi calling in your destination. Keeping the home line enabled can still incur charges even with data roaming off. If you do not need that number, switching the home line off avoids using it; otherwise use internet calling over your travel data and follow your carrier's advice.

Label your lines clearly (for example 'Home' and 'Travel') so you always know which one is which in your settings and dialler.

Hotspot and messaging apps

If you plan to share data with a laptop or a travel partner, check whether the plan allows hotspot use; it's listed on the plan page where the information is available. Messaging apps tied to your phone number keep working over the travel data line, because the number identifies your account rather than the network you're using.

Before you come home

When the trip ends, switch your mobile data line back to your home SIM and turn data roaming back off for the travel line. You don't need to delete the travel eSIM immediately — keeping it lets you check usage or add a top-up if you return to the same place, where top-ups are offered for that plan.