Unified Communication Across Devices even while traveling abroad - The Power of Apple ID for Calls and Messages
Using the same Apple ID on both your devices will have the following features concerning Calls and Text Messages.
Text Messages on other devices
On your iPhone, go to Settings > Messages > Text Message Forwarding. If you can't see Text Message Forwarding, go to Settings > Messages. Turn off iMessage, then turn it back on. Tap Send & Receive, tap Use Your Apple ID for iMessage, then sign in with the same Apple ID used on your other devices.
Forward SMS/MMS text messages from your iPhone to your ...
- Use the same Apple ID on both devices.
- Follow the process here --> How to forward SMS/MMS text messages from your iPhone to ...
Calls on other devices
Do any of the following: Tap Calls on Other Devices, turn on Allow Calls on Other Devices, then choose the devices on which you'd like to make and receive calls. This allows other devices where you're signed in with the same Apple ID to make and receive calls when they're near your iPhone and connected to Wi-Fi.
Allow phone calls on your iPad and Mac - Apple Support (IN)
Stop getting calls on other devices
To stop getting calls on one of your devices, just turn off the Calls from iPhone setting on that device. Watch the GIF below
Stay connected abroad without roaming charges! Use SMS/MMS texting and iMessage over Wi-Fi instead of enabling data roaming with your carrier.
Maximize the use of an unused iPhone during international travels. By leveraging iMessage and SMS over Wi-Fi, you can stay connected without relying on cellular data. Here's how:
Ensure the following pre-conditions are met:
Keep your primary iPhone with your India SIM card powered on and connected to a power source in India.
Use the same Apple ID across all your devices.
Consider the following devices and set up Text Message Forwarding before departing for international destinations.
Device D1 (iPhone) with Phone No. P1, Network Carrier C1
Device D2 (iPad)
Device D3 (Mac)
Device D4 (Another iPhone) with Phone No. P2, Network Carrier C2
Now, regardless of the device's (D2, D3, or D4) location or Wi-Fi network, you can seamlessly send and receive iMessages and SMS texts across continents. This means you can send SMS using P1 from devices D2, D3, or D4 from any international destination. (P1 with D1 should remain in India connected to the carrier network C1 and be powered on.)
In summary, leaving your iPhone in India while traveling abroad enables continuous iMessage and SMS communication using your Indian phone number. Even in the USA, recipients will perceive messages as originating from your phone number.