eSim on iPhone 11 for South Africa trip. Must swich off all calls & sms messages

If you have an old iPhone lying unused with you then the best would be to use it now. Then you can send and receive iMessage / SMS over WiFi you need not use cellular data. See the pcocess below...

It is possible with certain pre-conditions. Please read below...

For example, if you leave the SIM (UK) in the UK on another iPhone and keep it switched ON then this device can continue to send and receive iMessage and SMS from the same Phone number number to another iPhone having either only data SIM or complete SIM/ eSIM taken from the USA. Read more below...

Countries mentioned here are only as an example.

Yes, it will work. Different State/Country/Continent and different WiFI? No problems

1. Must use the same Apple ID.
2. Follow the process before leaving the country
3. The two devices need not be on the same WiFi.
4. Even if the devices are across different continents the iMessages will get delivered to all the devices with certain preconditions. You may read below

iMessage works in the following manner.

• Phone No. P1, Network Carrier C1, Device D1 (iPhone)
• Phone No. P2, Network Carrier C2, Device D2 (iPad with Cellular Service)
• Device D3 (Mac)

Following assumptions

All devices D1, D2 & D3 uses the same Apple ID

D1 > Settings > Messages > Text Message Forward > [Both D2 & D3 are enabled]

D1 > Settings > Messages > Send & Receive > P1 is Selected

D2 > Settings > Messages > Text Message Forward > [Both D1 & D3 are enabled]

D2 > Settings > Messages > Send & Receive > P2 is Selected

D3 > Messages > Preferences > iMessage > Start New Conversation from > P1 is Selected

You can send and receive iMessages as follows

• Send from P1 using D1 to any other iOS device across the globe. (P1 must remain in the same carrier network of C1 or have international roaming enabled using P1)
• Send from P2 using D2 to any other iOS device across the globe. (P2 must remain in the same carrier network of C2 or have international roaming enabled using P2)
• Send from P1 using D3 to any other iOS device across the globe. (P1 must remain the same carrier network of C1 or have international roaming enabled using P1)
• Device D3 can send and receive iMessage using P1 being anywhere in the globe under any WiFi network but (P1 must remain the same carrier network or have international roaming enabled using P1)
• Can send iMessage using Apple ID anytime anywhere any device

In a nutshell

If I have a Phone Number from India on my iPhone and I travel to the USA without international roaming enabled., my iPhone will seize to send messages using the number I had.

But If I leave the iPhone in India (Powered) and travel with my Mac to the USA, I can continue to send and receive iMessages / SMS using the same phone number I had, from the USA. The recipients will receive it as though it is being sent from my Phone number.

I Hope, I have been able to make things clear.

If you don't enable international roaming before leaving your country for a holiday, your iPhone with eSIM won't allow you to make or receive calls, and this is also true for messages. International roaming must be enabled to use your phone's cellular services outside your home country. Without it, your device won't be able to connect to foreign networks, resulting in restricted communication capabilities. To avoid any disruptions during your travels, make sure to activate international roaming for your eSIM before departing.

While you won't be able to make or receive regular cellular calls or messages without international roaming, WhatsApp will still function over WiFi. WhatsApp uses an internet connection (WiFi or cellular data) to send and receive messages, so as long as you have a WiFi connection, you can continue to use WhatsApp to chat with friends and family even without enabling international roaming.

However, it's important to note that if you change your phone number or SIM card on your iPhone, WhatsApp will indeed cease to work with your old number. WhatsApp is tied to your phone number, and when you change it, the app will prompt you to verify the new number. If you don't verify the new number, you won't be able to continue using WhatsApp with your old account and chat history. So, in such cases, it's essential to follow WhatsApp's verification process with the new number to continue using the app seamlessly.

I went on holiday to south Africa, but when I come back to Australia and receive calls my iphone 11, the incoming Australian phone numbers show up with the South African +27 prefix instead of the Australian +61 prefix? So if I want to reject the incoming call and try to send a text msg about calling them back, the message fails because the phone number has the +27 prefix. I then have to go into my contacts, find the person and send them a msg after about calling them back.