Dual sim mode and iMessage

Hi guys,

I've set up my iPhone 12 Pro today using my Vodafone UK account (my home account) as my eSim allowing me to use the SIM card slot with a foreign sim (for the sake of testing, I'm using my Vodafone GR account).

What I noticed is that whilst it was easy to set up the service and it seems pretty easy to select what line does what, it appears that toggling the switch to off for either line automatically removes it from iMessage.

If you then switch that line back on, you get the text message saying 'Activate iMessage'.

Is there no way of keeping iMessage registered and active? I mean iMessage isn't deactivated when I put a phone into airplane mode.

The reason why this is an issue is (1) any messages sent to my number when that line is switched off won't deliver as an iMessage but more importantly, it completely undoes the reason why I want to utilise dual sim.

So (assuming COVID doesn't stop me), I'll be going on vacation to the far-East for a month at the end of December.

I had in my mind that I would use my home simcard as e-Sim but have data roaming switched completely switched off. I would still want it linked to iMessage so I could receive texts and iMessages. I'd then use a local SIM card in the other slot for mobile data and outgoing calls.

The problem for me would be, if I wanted to switch off my home line at any point (by toggling to off) for a period of time then it would ultimately want to send a text message every time I switch the line back on. That one text (with my home operator) would generate the daily roaming charge of 6 GBP ($8).

So I'd like iMessage to stay active unless I removed the sim from the phone.

Hope I've articulated this clearly.