Last updated: September 13, 2026
"I've set up a US phone number through an app, but I'm planning to use a data-only eSIM while I'm there. Will calls and texts actually work?" Plenty of travelers get stuck on exactly this question before departure. This guide walks first-timers through how a US number app and a data-only eSIM work together, step by step.
The short answer: US number apps send and receive calls and texts over the internet (a data connection), so they work on nothing more than the data from a data-only eSIM. The eSIM itself doesn't need a phone number or SMS capability.
- Number apps run entirely on a data connection
- Your eSIM doesn't need its own number or SMS
- Register at home first, then switch on data after you land
- If calls don't come through, check your connection and notifications first
- Your data allowance depends on video and maps, not calls
How a US Number App Works on Data Alone
A US number app is a service that gives you a US phone number inside an app and handles calls and texts over the internet. Unlike a traditional mobile line, where the number is tied to a SIM card, the number is tied to your app account. As long as your phone has an internet connection, you can use the same number on any network.
In other words, all you need is a stable data connection. Whether that's your home Wi-Fi or a data-only eSIM at your destination, the app simply sees a phone that's online. That's why number apps and data-only eSIMs pair so well.
Still choosing an app? Narrow down your options first
If you haven't decided which app to get your number from, start with Apps That Give You a US Phone Number Before You Travel: How to Choose, which compares options by use case. Once you've picked one, the steps in this article apply directly. Here we focus on the stage after you've chosen an app: actually using it alongside your eSIM.
Data-Only eSIM + Number App: What Works and What Doesn't
In brief: calls and texts through the number app work; voice calls and SMS on the eSIM's own line do not. It's easy to mix these up and assume "no voice calls means the app won't work either," so here's a clear breakdown.
| What you want to do | On a data-only eSIM | Notes |
|---|---|---|
| Make and receive calls from your US number in the app | Yes | Make sure the app is set to route calls over the data connection |
| Send and receive SMS in the number app | Yes | Works as the app's built-in messaging feature |
| Calls on WhatsApp, Messenger, FaceTime, and similar apps | Yes | Any calling that uses data works as usual |
| Voice calls on the eSIM's own line number | No | Bloomy plans are data-only as standard |
| Receiving SMS on the eSIM's own line number | No | If you need verification texts, use your number app or another method |
To sum up, the only things you can't do are voice calls and SMS on the phone number assigned to the eSIM itself. App-based calling on WhatsApp, Messenger, FaceTime, and the like, plus calls and texts through your number app, all work normally. A natural split is WhatsApp for family and friends back home, and your number app for local restaurants, hotels, and bookings.
What to Do Before You Leave Home (Registration and Testing)
In brief: get your number and test the app on Wi-Fi at home before you travel. If you leave the initial setup until after you arrive, it's much harder to deal calmly with verification hiccups or unfamiliar prompts in the app.
- Install the number app and register. Some apps ask for identity verification or a code sent to an existing phone number during sign-up. Requirements vary by app, so check the latest details in each app's official documentation.
- Check the call routing setting. Some apps let you choose whether calls go over the data connection (internet) or over your mobile carrier's voice line. Since you'll be on a data-only eSIM, choose data / internet.
- Allow notifications. Incoming calls and texts arrive as app notifications. If notifications are off, you simply won't notice calls coming in.
- Make a test call on Wi-Fi. Call a family member or your own second contact method to confirm that audio goes through and incoming calls ring.
- Buy your eSIM and add it to your phone with the one-tap setup link. With Bloomy, you just tap the setup link you receive and follow the on-screen prompts. You can wait until you've landed to turn the line on.
If you're unsure about adding the eSIM, our setup guide walks through the screens step by step.
Getting Up and Running at Your Destination
In brief: once you arrive, there are three things to do: turn on the eSIM line, confirm data is working, and open your number app.
- After landing, go into Settings, turn on the eSIM line, and select it as your mobile data line.
- Open any page in your browser to confirm the data connection is working.
- Open your number app and check that its status shows online or connected. The display varies by app, but if the call button is active, you're generally good to go.
- If you want extra reassurance, send one test call or text to someone back home. That also confirms the receiving side works.
When you're on a data-only eSIM, the "Default Voice Line" setting on iPhone or the "SIM for calls" setting on Android has no direct effect on your number app. Because the app runs purely on data, all you need to check is that your mobile data line is set to the eSIM.
What to Check When Calls Don't Come Through or Keep Dropping
In brief: when a number app misbehaves, the cause is usually one of three things: the data connection, notifications, or the app's own settings. Working through them in order makes it easier to isolate the problem.
1. Is the data connection itself working?
If your browser or WhatsApp isn't working either, the issue is with the eSIM connection, not the number app. Toggle Airplane Mode off and on, check your data roaming setting, and confirm which line is selected. For detailed troubleshooting, see our connection troubleshooting page.
2. Are notifications and background activity allowed?
If the app's notifications are turned off, or a battery-saver setting has stopped it from running in the background, you won't be alerted to incoming calls. Check the app's notification and battery settings in your phone's Settings.
3. The app's call routing setting
If the app is set to route calls over your carrier's voice line, you may not be able to place calls on a data-only eSIM. Switch it to data / internet.
4. Audio dropouts caused by network quality
Choppy audio comes down to the local network's coverage, congestion, and signal conditions inside buildings. This can happen regardless of which eSIM you use, and moving to a different spot or switching to Wi-Fi often helps.
Who This Setup Is (and Isn't) Right For
In brief: it suits people who mostly call through apps and only occasionally need a US number for local businesses or bookings. It doesn't suit anyone who needs a true voice line.
A good fit if you...
- Are traveling or staying short-term and need a US number occasionally for hotels, restaurants, or ride-hailing
- Are starting a study-abroad program or a longer stay and want one local number to begin with
- Keep in touch with family and friends back home over WhatsApp or similar apps
- Want to consolidate your connectivity costs into a single data plan and pay only for what you need
Not a good fit, or worth considering alternatives, if you...
- Need top-priority voice-line quality for work and don't want to depend on a data connection
- Plan to use many local services that require SMS verification to a number tied to a SIM
- Need line-based calling for purposes such as emergency calls
If you'll need a number or SMS for a wide range of things, it's worth also looking into a local SIM with voice or checking whether a plan with a number is available. You'll find more on this topic in our phone number and SMS category.
Choosing an eSIM to Pair with Your Number App
In brief: size your data allowance around maps, social media, and video, not calls. App calling generally uses far less data than streaming video, but consumption depends on the app, audio quality settings, and how long you talk, so leave yourself some headroom.
- Duration: Pick a plan slightly longer than your stay, so a shifted return date or a long wait at the airport doesn't catch you out.
- Data: Base it on how much you'll use maps, share photos, and watch video. If calls are your main use, a modest allowance is often enough; heavy video watchers should go bigger.
- Unlimited or standard: Even unlimited plans may come with a fair-use policy, reduced speeds after a certain amount of usage, or tethering conditions. They're well suited to heavy daily use, but check the terms before you buy.
You can browse US plans on the Bloomy eSIM comparison page by country, data allowance, and number of days. Available plans, prices (in USD), and terms may change over time, so please check the latest details at the time of purchase. Bloomy plans are data-only (no phone number, SMS, or voice calls), and actual speeds and coverage depend on the local network, your device, and your location.
Summary: Set Up Your Number at Home, Then Just Turn On Data When You Land
Because US number apps run on data, calls and texts through the app work fine alongside a data-only eSIM. The only things that don't work are voice calls and SMS on the eSIM's own line number; app calling on WhatsApp and similar services works exactly as usual.
There are three things to do: (1) register and test the number app on Wi-Fi at home, (2) tap the eSIM setup link to add it to your phone, and (3) turn on the line after you arrive and open the number app. If calls aren't coming through, check your data connection, then notifications, then the app's call routing setting, in that order.
Want to revisit which app to use? See our guide to choosing a US number app. For questions about purchasing or setup, visit our FAQ.
* The information in this article is current as of September 2026. Registration requirements and features of number apps, as well as eSIM plan details and terms, are subject to change. Please check each app's official documentation and the comparison page for the latest information.
