iPhone Choose Line for Texts with Dual SIM

iPhone How to Choose a Line for Text Messages with Dual SIM.

Learn how to select which line to use when sending text messages on an iPhone with multiple SIMs. If you use a physical SIM and an eSIM together, this helps you control which number appears as the sender.

I will show you this on an iPhone 16 Pro Max running iOS 26 Beta 6. The steps are the same on most iPhone models with Dual SIM support.

How to tell which line you are using in a conversation

When you have two SIM cards active, your iPhone shows you which line each conversation is using.

Open the Messages app. Look at your list of conversations. Next to each text message thread, there is a small label. This shows you which SIM card you are using for that conversation.

In the video example:

• P means Primary (the main line)
• S means Secondary (the second line)

If you have given your lines custom labels (like “”Personal”” and “”Work””), those labels will appear instead.

How to choose a line for a new conversation

When you start a new text conversation with someone you have never messaged before, you can pick which line to use.

Step 1: Open the Messages app

Step 2: Tap the new message icon in the top right corner (square with a pencil or plus sign)

Step 3: Enter the contact name or phone number

Step 4: A popup will appear asking which line you want to use (Primary or Secondary)

Step 5: Tap the line you want

Step 6: Type your message and tap Send

The conversation will now use that line. You will see the line label next to the conversation in your messages list.

How to change the line for an existing conversation

If you already have a conversation with someone and want to switch to your other number, you can change it.

Step 1: Open the Messages app

Step 2: Tap on the conversation you want to change

Step 3: At the top of the conversation, tap the current line label (it shows which line you are using)

Step 4: A menu will pop up showing your available lines

Step 5: Tap the line you want to switch to

Step 6: The conversation now uses the new line. Any messages you send from now on will come from that number.

The old messages stay in the conversation. Only new messages are affected.

What happens when you change the line

When you change the line for a conversation, your iPhone does not delete any previous messages. The old messages remain visible. They still show which line was used for each message (you can see the label in the message bubbles).

Only future messages that you send will use the new line.

How to set your default line for new messages

You can choose which line your iPhone uses by default when you start a new conversation.

Step 1: Open Settings

Step 2: Tap Messages

Step 3: Tap “”Send & Receive””

Step 4: Under “”Start New Conversations From,”” you will see your phone numbers

Step 5: Tap the number you want to use as your default

Now when you start a new conversation with someone not in your contacts or someone you have never messaged before, your iPhone will automatically use this line.

How to identify which line you are using in a conversation

There are two ways to check:

Method 1 – Look at the conversation list:

• Open Messages
• Look at the small label next to each conversation
• The label shows the current line for that conversation

Method 2 – Look inside the conversation:

• Open the conversation
• Look at the top of the screen where the contact name is
• The line label appears next to or below the contact name

How to label your SIM cards

Give your SIM cards clear names so you know which is which.

Step 1: Open Settings

Step 2: Tap Cellular or Mobile Service

Step 3: Tap on each SIM (Primary, Secondary, etc.)

Step 4: Tap “”Cellular Plan Label””

Step 5: Choose from the list (Personal, Business, Travel) or tap “”Custom Label”” to type your own

Step 6: Enter your custom label and tap Done

Now when you choose a line for messages, you will see your custom labels instead of just Primary and Secondary.

Does this work for phone calls too?

Yes. When you make a phone call on an iPhone with Dual SIM, you can also choose which line to use.

• For new calls: You can pick the line before dialing
• For existing contacts: Your iPhone may remember which line you used last

The process is similar to messages.

What about iMessage vs SMS

The line selection works for both iMessage (blue bubbles) and SMS/MMS (green bubbles). The steps are exactly the same regardless of what type of message you are sending.

Can you change the line for a group conversation

Yes. The same steps work for group conversations. Tap the line label at the top of the group chat to switch to a different line.

Quick summary

To choose a line for a new conversation:

1. Open Messages
2. Tap the new message icon
3. Enter the contact name or number
4. Tap the line you want to use (Primary or Secondary)
5. Type and send your message

To change the line for an existing conversation:

1. Open the conversation
2. Tap the line label at the top
3. Tap the new line you want to use
4. Future messages will use the new line

To set your default line for new conversations:

1. Settings > Messages > Send & Receive
2. Under “”Start New Conversations From,”” tap your preferred number

To label your SIM cards clearly:

1. Settings > Cellular
2. Tap each SIM
3. Tap “”Cellular Plan Label””
4. Choose or type a custom label

Things to remember:

• The line label appears next to each conversation in your messages list
• Changing the line for a conversation does not delete old messages
• Only new messages use the new line
• You can switch lines as many times as you want

Thanks for watching. Dual SIM messaging is very useful when you travel or when you have separate personal and work numbers. Now you know exactly how to choose which number sends your messages.