Do I Turn Off My Primary Line When Using eSIM?

Let’s face it—figuring out how to manage your phone service while traveling internationally can be… well, complicated.

If you’ve recently embraced the convenience of eSIM technology, you’re probably wondering if you should turn off your primary phone line while using that shiny new digital SIM card.

The short answer? Yes, in most situations, you absolutely should turn off your primary line when using an eSIM abroad. But—and there’s always a but—there are some nuanced scenarios where keeping both active might make sense.

Let’s dive into the why, when, and how of managing your dual connectivity situation.

Understanding How Your Primary Line and eSIM Work Together

Modern smartphones are pretty clever. They can juggle multiple connections simultaneously, which is both convenient and potentially costly. When your phone has both your primary SIM and an eSIM activated at the same time, here’s what’s happening behind the scenes:

• Your phone maintains connections to both networks
• One line is designated as the primary data connection (this is important!)
• The other line stays active for calls and texts
• Your phone constantly communicates with both carriers’ networks

This dual connectivity is impressive technology, but it creates a situation where—without you doing anything—your primary line might be quietly racking up charges while you think you’re safely using your travel eSIM.

Why You Should Usually Turn Off Your Primary Line

Those Sneaky Roaming Charges

The biggest and most compelling reason to disable your primary line is financial. International roaming charges can be absolutely brutal.

Even when you’re actively using your travel eSIM for data, your primary SIM might still be:

• Receiving push notifications
• Checking for voicemails
• Downloading email headers
• Running background app processes
• Connecting periodically to maintain service

And each of these seemingly innocent activities can trigger data usage on your primary line—sometimes at rates of $10-15 per megabyte! I’ve seen horror stories of travelers coming home to $1,000+ phone bills for data they didn’t even know they were using.

Technical Advantages of Single-Line Operation

Beyond avoiding bill shock, there are practical benefits to running just your eSIM:

• Better battery life: Managing two active connections drains your battery faster
• Clearer connection experience: No confusion about which network is handling what
• Simplified notifications: Avoiding duplicate alerts from two different carriers
• Reduced connection switching: Prevents your phone from jumping between networks

When You Might Want to Keep Your Primary Line Active

Despite the risks, there are legitimate reasons why some travelers choose to keep their primary line active alongside their eSIM:

Staying Reachable on Your Main Number

If people absolutely need to reach you on your regular number—perhaps for work emergencies or family situations—completely disabling your primary line means missing those calls.

In these cases, consider:

• Setting up call forwarding to a VoIP service
• Using messaging apps that work over data
• Checking your primary line periodically in a controlled manner
• Using Wi-Fi calling features if your carrier supports them

Professional Requirements

Some professions require constant availability. If you’re a doctor on call, a key decision-maker in your organization, or someone who simply can’t afford to miss communications, the cost of keeping your primary line active might be justified.

How to avoid roaming charges while traveling has some great specific strategies for these situations.

The Practical Guide: Managing Your Lines Effectively

Here’s how to actually implement this advice on your device:

For iPhone Users:

1. Go to Settings > Cellular
2. Select your primary SIM
3. Toggle “Turn on this line” to off
4. Your eSIM will remain active while your primary SIM is disabled

For Android Users:

1. Go to Settings > Network & Internet > SIMs
2. Find your primary SIM card
3. Toggle it off while leaving your eSIM enabled
4. Some phones may have slightly different menu paths

Smart Scheduling Strategies

If you need to periodically check your primary line:

• Set a specific time each day to briefly enable your primary SIM
• Use airplane mode, then selectively enable just Wi-Fi and your eSIM most of the time
• Consider whether your critical contacts could reach you via messaging apps instead

Making the Right Choice for Your Situation

The decision ultimately comes down to your specific needs. Consider:

• How critical is constant accessibility on your primary number?
• What would be the financial impact of potential roaming charges?
• Are there alternative communication methods that could work for you?
• How long will you be traveling?

For most casual travelers, completely disabling your primary line and relying on your travel eSIM is the safest approach. Many travelers find that an eSIM is absolutely worth it for travel compared to international plans from their home carriers.

Modern eSIMs, like those from eSIM4, connect automatically when you arrive at your destination and provide reliable data service in over 200 countries. This means you can still use messaging apps, make internet calls, and stay connected without the risk of accidental roaming charges.

The Technical Explanation: How Data Actually Works

Here’s where things get a bit technical—but understanding this can save you significant money.

When your phone has two active lines (your primary and eSIM), it designates one as the data line. Even if you’ve set your eSIM as the primary data line, your phone will still maintain an active connection to your home carrier’s network. Various system processes may still attempt to use that connection for small data transfers.

Think of it like having two faucets that can both run water. Even if you’re primarily using one, the other might occasionally drip—and those drips can be very expensive when you’re roaming internationally.

A Smart Middle Ground

If you’re worried about missing important communications, consider this balanced approach:

1. Disable your primary line’s data roaming specifically (not the entire line)
2. Enable Wi-Fi calling if your carrier supports it
3. Use your eSIM for all data needs
4. Inform important contacts about your alternative contact methods

This setup allows calls and texts to reach your primary number (usually at a more reasonable rate than data) while preventing costly data usage. It’s not perfect—you’ll still pay for incoming texts and calls—but it’s better than leaving everything enabled.

You can find more details about avoiding roaming charges on cruises and in other specific travel situations if you have special travel plans.

The Bottom Line

For most travelers, the simplest and safest approach is:

• Turn off your primary line completely
• Rely on your travel eSIM for all connectivity
• Use internet-based communication apps
• Set up alternative contact methods before you leave

If you absolutely must remain reachable on your primary number, be strategic about how and when you enable it, and be prepared for some additional charges—just not the shocking bills that come from uncontrolled data roaming.

By taking a few minutes to properly configure your phone before traveling, you can enjoy the convenience of staying connected without the stress of wondering what surprise might be waiting in your next phone bill.

Thinking about purchasing an eSIM online? See our eSIM packages here.