Quick answer
Keep your regular SIM in your phone and use the travel eSIM only for mobile data. WhatsApp stays on your usual number, because it works over whatever internet connection your phone has. Turn data roaming off on your regular line so your home carrier doesn't charge you for data.
Why WhatsApp keeps your number
WhatsApp uses your phone's internet connection, the same way web browsing and email do. It doesn't matter which line that connection comes from: WhatsApp says you can still use it with your home number when you use a different SIM while travelling.
Burj eSIMs are data only and have no phone number, so there's nothing to switch in WhatsApp. Your contacts keep seeing your usual number.
Set up your iPhone
- Go to Settings → Cellular → Cellular Data and choose the Burj line. Your iPhone uses one line for data at a time.
- Keep your regular line turned on, so you can still receive calls and SMS on your number.
- Go to Settings → Cellular, tap your regular line, and turn Data Roaming off.
- Tap the Burj line and turn Data Roaming on.
Your iPhone also lets you choose which numbers iMessage and FaceTime use. Keep your regular number selected for both.
Set up your Android phone
Open your phone's SIM settings (on Samsung Galaxy: Settings → Connections → SIM manager). Choose the Burj eSIM for mobile data, keep your regular SIM for calls and SMS, and turn roaming off for your regular SIM. Menu names differ between phone makers.
Calls and SMS on your regular number
With your regular line on, calls and SMS to your number still reach you abroad. Your home carrier may charge roaming rates for them, so check with your carrier before you travel. WhatsApp calls and messages go over the Burj eSIM's data instead.
If WhatsApp asks you to verify again
WhatsApp sends its verification code to your number by SMS or call. To receive it abroad, your regular SIM has to be in your phone with its line turned on, and your carrier may charge roaming rates for that SMS or call. Keep your regular SIM in the phone for the whole trip.
Before you travel, add an email address to your account in WhatsApp's settings. If you ever need to register your number again, WhatsApp can then send the code by email. And avoid reinstalling WhatsApp or moving it to a new phone while you're away.
Common questions
Will my WhatsApp contacts see a different number?
No. Burj eSIMs have no phone number, and WhatsApp stays on the number you registered it with.
Do I need to take my regular SIM out?
No. Keep it in your phone. Your phone can use your regular SIM and the Burj eSIM at the same time, and you need it if WhatsApp asks you to verify your number.
Can I still receive calls on my number while abroad?
Yes, as long as your regular line is turned on. Your carrier may charge roaming rates for calls and SMS, so check with them before you travel.