How to switch between your physical SIM and eSIM

Switching between your physical SIM and your eSIM is two taps in Settings, not a hardware swap. Both lines stay installed at the same time. You're just changing which one your phone uses for cellular data, voice calls, or messages. The flip is reversible at any moment. Useful when you fly home and want your home plan's data back, or when you travel and want Eflexsim to take over.

Below: the four switches that actually matter, how to make each on iPhone and Android, and the common mistakes that cause "I switched but nothing changed" confusion.

What you can actually switch

There are four independent settings on a dual SIM phone:

• Mobile data line. Which line provides internet to apps and Safari/Chrome.
• Default voice line. Which line your phone uses when you tap a number in Contacts or dial from the keypad.
• Default SMS line. Which line outgoing texts use.
• Per-contact line. You can override the defaults for specific contacts (call Mom on the home line, call your travel companion on Eflexsim's data line via WhatsApp).

Most travelers only flip the mobile data line. Eflexsim becomes your data on arrival, your home line stays available for calls and SMS without using its data. When you fly home, you switch mobile data back to your home line.

The other three switches matter less because Eflexsim is data-only. It doesn't have a callable number for the voice or SMS lines to use. Your home line stays the default for both regardless.

How to switch on iPhone

iPhone groups these settings under Settings → Cellular.

Switch the data line:

1. Open Settings.
2. Tap Cellular.
3. Tap Cellular Data (near the top).
4. Pick the line you want for data. Your home line or Eflexsim.

That's it. The change applies immediately. Open Safari or Maps to confirm. If the page loads, you're on the new data line.

Switch the default voice line (rare with Eflexsim, since it's data-only, but useful if you have a second voice line):

1. Settings → Cellular → Default Voice Line.
2. Pick the line.

Set a per-contact line:

1. Open the Contacts app.
2. Tap the contact you want to override.
3. Tap Edit → scroll to Preferred Cellular Plan → pick the line.
4. Tap Done. That contact's calls now route through the chosen line by default.

Turn the Eflexsim line on or off temporarily:

1. Settings → Cellular.
2. Tap the Eflexsim line (under "SIMs").
3. Toggle Turn On This Line off.

Turning the line off doesn't delete it. The eSIM stays installed, and the timer doesn't reset. Toggle the line back on whenever you want to use it again.

How to switch on Android

Android's labels vary by manufacturer, but the controls are equivalent.

Samsung Galaxy:

1. Settings → Connections → SIM manager.
2. Under Preferred SIMs, set Mobile data to Eflexsim (or your home line).
3. Calls and Messages have their own dropdowns. Set them to your home line for voice/SMS as usual.

Google Pixel:

1. Settings → Network & internet → SIMs.
2. Tap the SIM you want as your data line.
3. Toggle Use SIM for mobile data on, or tap Mobile data preference and pick your line.

OnePlus / Motorola / Oppo / Sony / others:

1. Open Settings and search "SIM" or "Dual SIM".
2. Find the setting labeled "Preferred SIM for data" or "Mobile data SIM."
3. Switch to Eflexsim.

Turn the Eflexsim line on or off:

• Samsung: SIM manager → Eflexsim row → toggle off the line. The line shows as inactive without deleting the profile.
• Pixel: Settings → Network & internet → SIMs → Eflexsim → toggle Use SIM off.
• Other Android: Settings → SIM cards → tap Eflexsim → toggle disable.

Same as iPhone, disabling the line doesn't delete it. The profile stays installed and the validity timer continues running (we explain timer behavior in how long does my data plan last).

The common mistake: changing the data line without enabling roaming

The most frequent "I switched but it didn't work" complaint isn't actually about switching. It's about Data Roaming. iPhone and Android label international data as "roaming" even on a travel eSIM that's a partner network's local carrier. If the Eflexsim line's Data Roaming toggle is off, you can switch to it as your data line and still get no internet.

Fix on iPhone:

1. Settings → Cellular → tap the Eflexsim line.
2. Toggle Data Roaming on.

Fix on Android:

1. Settings → SIM cards → tap Eflexsim.
2. Toggle Data roaming or Mobile data while roaming on.

If you switch to Eflexsim and don't see data flowing within a minute, this is almost always the cause.

What stays the same when you switch

A few things people worry about that don't actually change when you flip lines:

• WhatsApp and other internet messaging apps keep working regardless. They route over whichever line has data, so messages send and receive without you reconfiguring anything.
• Your home phone number stays attached to your home line. Switching the data line doesn't move or affect your number.
• iMessage and FaceTime continue to use your home line's Apple ID registration. Texts to other Apple users still arrive blue-bubbled at your home number.
• Stored Wi-Fi networks are device-wide. Switching SIMs doesn't change which Wi-Fi networks your phone knows.
• Installed apps and their logins are device-wide. Switching SIMs doesn't sign you out of anything.

The only thing that really changes is which line carries your cellular data.

When to switch back to your home line

The natural switching moments:

• On arrival abroad. Switch from home to Eflexsim.
• On the flight home. Leave it on Eflexsim until you've landed (or switch in the cabin during descent if you want a head start).
• After landing home. Switch from Eflexsim back to your home line. Disable the Eflexsim line in Cellular settings so it doesn't accidentally use any remaining plan time.

You can also switch mid-trip if you cross between coverage areas. For example, if your Eflexsim plan covers Italy and France but you take a day trip to a non-covered country, switch to your home line temporarily (accepting your home carrier's roaming charges) and switch back when you return to a covered area.

Frequently asked questions

QWill switching the data line drop my call?

No. Switching the data line affects only data routing. Calls in progress continue on whatever line they started on. New calls follow your default voice line setting.

QDoes switching the data line affect my home line's signal?

No. Both lines stay registered with their respective networks independently. The data switch is purely a routing choice inside your phone, not a network-level handover.

QCan I switch the data line automatically based on which one has a better signal?

On most modern Androids, yes. Samsung calls it "Smart Network Switch," Pixel calls it "Auto-Switch Data SIM." iPhone doesn't have this; you switch manually. For travel, manual switching is usually fine. You flip when you cross a border, not constantly throughout the day.

QWhat if I switch to Eflexsim and forget to switch back when I'm home?

The Eflexsim plan keeps using its remaining time until it expires. You wouldn't have data at home (the plan doesn't work in your home country), so you'd notice quickly. Switch back in two taps.

QCan I have data on one line and Wi-Fi calling on another?

Yes. Wi-Fi calling lives on whichever line you enable it on, independent of the data line. If you turn on Wi-Fi calling for your home line, calls go through your home number over hotel Wi-Fi while Eflexsim handles cellular data.

If you want both lines visible all the time, the dual SIM vs eSIM guide covers the underlying setup. If you're seeing errors after switching, check the no signal troubleshooting guide.