Travel eSIMs and iMessage/RCS

[japtor]

There's this Apple doc on dual SIM use, but just want to make sure on certain details:

https://support.apple.com/en-us/109317

I'm going on a little trip and figuring I'd save some money with a cheap data only eSIM. But want to still keep my phone number active for emergency calls or texts (...or particularly annoying 2FA/security messages that only go through SMS).

Main thing I'm wondering is if someone iMessage or RCS capable messages my normal phone number, would the messages be delivered through my travel data only SIM, or through my normal SIM over SMS? Same thing goes with outgoing messages. The Apple doc just mentions selecting which number to send with, but can't tell if it'd route through the travel SIM (if iMessage or RCS of course). I'd have my normal number have data disabled and data switching turned off, so theoretically anything data should go through the travel SIM (going by the Apple instructions at least).

 

[kefkafloyd]

I did this in Japan last year. Had data roaming off, data disabled on my US line, and wifi calling enabled for my US line. iMessage will use whatever data coonnection you have. Didn't get a single overage on AT&T. Receiving SMS was free but sending would've incurred a charge.

I don't know about RCS but since it's a data connection I don't see why it wouldn't behave the same way.

 

[japtor]

Ah wifi calling was another aspect I was wondering about, do calls fallback to the data/travel SIM? I was never sure if actually needed wifi specifically or just any data connection. I guess SMS technically works over wifi calling too, I tested it out a while back for another trip, so hopefully that'd work over the SIM too if that's the case.

 

[byrningman]

I’m doing this now and it seems to work fine. Crucially, I get 2FA messages destined for my home SIM that does not have data roaming activated. Game changer for me.

 

[kefkafloyd]

Ah wifi calling was another aspect I was wondering about, do calls fallback to the data/travel SIM? I was never sure if actually needed wifi specifically or just any data connection. I guess SMS technically works over wifi calling too, I tested it out a while back for another trip, so hopefully that'd work over the SIM too if that's the case.

Wifi calling only works over Wifi, IIRC.

 

[japtor]

Wifi calling only works over Wifi, IIRC.

Dang ok well that's what I always figured but was hopeful. Calling isn't a huge concern but incoming SMS is still something like 5 cents on Verizon. Not too concerned there since most stuff should be iMessage/RCS but would be nice to not worry about it.

I guess the alternative would be a mobile hotspot and just stay on wifi everywhere?

 

[kefkafloyd]

Dang ok well that's what I always figured but was hopeful. Calling isn't a huge concern but incoming SMS is still something like 5 cents on Verizon. Not too concerned there since most stuff should be iMessage/RCS but would be nice to not worry about it.

I guess the alternative would be a mobile hotspot and just stay on wifi everywhere?

That's what people used to do before these easy eSIMs, yeah.