"Set up your default voice line" — what to choose

During eSIM install, iPhone shows a prompt called "Set Up Your Default Voice Line" with both lines listed. Pick your home line. The default voice line is what iPhone uses when you tap a phone number in Contacts or dial from the keypad. For Eflexsim travel use, that should be your home number because Eflexsim is data-only and doesn't have a callable phone number anyway. You can change this later in Settings without reinstalling.

Below: what the prompt actually controls, why your home line is almost always the right pick, and how to change it after install.

What the prompt is asking

iPhone shows this dialog only on phones with two cellular lines active. It's asking which line should be the default for:

• Outbound dialed phone calls (tapping a number in Contacts, or dialing from the keypad).
• Outbound SMS (a separate prompt handles this, but Default Voice Line affects it indirectly).
• Default "Caller ID". Which of your numbers shows up on the recipient's phone when you call.

The prompt does NOT affect:

• Inbound calls. Each line receives calls on its own number independently.
• Internet-based calls. FaceTime, WhatsApp, Signal, Telegram all route over data, not over the default voice line.
• Cellular Data line preference. That's a separate setting picked elsewhere.

So this prompt is specifically about outbound calling identity. Which of your two numbers should appear when you call out?

Why your home line is the right answer

Three reasons.

1. Eflexsim is data-only. Travel eSIMs (Eflexsim and most others) don't provide voice service. There's no callable phone number tied to your Eflexsim line. If you set Eflexsim as your default voice line, calls would fail because the line has no voice capability.

2. Your home number is what your contacts know. If you call your friend from your travel eSIM (which would be impossible anyway), they'd see an unknown number. Not your home identity. Default Voice Line keeps your number consistent with what people expect.

3. SMS delivery follows the voice line. Outgoing texts from the Messages app use the default SMS line, which iOS usually ties to the default voice line. Your home number is the SMS identity you want abroad too.

For 100% of travel eSIM users on Eflexsim, the right answer to this prompt is "my home line."

How the prompt looks during install

The exact wording on iOS 17/18:

Set Up Your Default Voice Line

Choose your default line for phone calls.

○ Personal - [your home phone number] ● Eflexsim - [no number, data-only]

[Continue]

Depending on your iOS version and how your lines are labeled, the wording shifts slightly. The structure is consistent: two radio buttons, pick one, continue.

iPhone defaults the selection to your most recently used line, which might be Eflexsim if you just installed it. Tap your home line before tapping Continue. If you accidentally pick Eflexsim, you can change it later (see below) but the install flow is smoothest if you get it right the first time.

How to change after install

If you tapped through the prompt without thinking, or you want to change the default later:

1. Open Settings → Cellular.
2. Tap Default Voice Line.
3. Pick the line you want. Usually your home line.
4. The change applies immediately. No restart needed.

You can also set per-contact preferences for specific people. In Contacts, edit a contact, scroll to "Preferred Cellular Plan," and pick the line you want for calls to that contact. Useful if you want family on your home line but a specific work contact routed differently (rare for travel eSIM users, but the option exists).

What if your phone has two voice-capable lines

The prompt becomes meaningful when both lines support voice. For example, two regular carrier eSIMs, or a physical SIM plus a regular carrier eSIM. In that case:

• Set the line you call from most often as the default.
• Outbound calls from Contacts or the keypad use that line unless you long-press the call button to pick the other one.
• The other line still receives inbound calls; it just isn't the default outbound.

For Eflexsim, this scenario doesn't apply because Eflexsim doesn't support voice. The prompt effectively has only one valid answer.

A note on iMessage and FaceTime

iMessage and FaceTime have their own settings under Settings → Messages and Settings → FaceTime. They aren't tied to the default voice line. You pick which phone numbers and Apple ID addresses can send/receive iMessage and FaceTime independently.

For Eflexsim users:

• Leave iMessage on your home number and your Apple ID.
• Don't enable iMessage on the Eflexsim line. Eflexsim doesn't provide an iMessage-capable phone number, and trying to enable it fails.
• FaceTime works the same way. Leave it on your home identity.

This means your iMessage threads continue to use your home number while abroad. Friends and family see messages from your normal number, not from Eflexsim.

For more on setting up dual-SIM cleanly, see iPhone install and choosing the default voice and data line on iOS. For Android equivalents, see Pixel install and Samsung install.