Unauthoritative Pronouncements

Dan Moren, and Jason Snell both traveled to the UK for the Relay anniversary event, and each of them spent some time beforehand in Scotland. I like to compare notes about travel stuff, because some of it is insightful for the next time I plan on going anywhere. A lot of the stuff I do is just the momentum of past decisions that I ultimately won’t research from scratch right before every trip, but I do absorb these sorts of blog posts throughout the year. Here are my own posts about travel tech in late 2023, advocating for a “travel mode”, and another post from this spring.

Both Dan and Jason were tripped up by iMessage abroad when they switched to their eSIMs. Long ago, my boyfriend and I decided that we’re more comfortable trading money for convenience so we do pay the daily flat rate that our carriers offer so we’ve never tried to do this.

The iMessage issues haven’t ruined Dan and Jason’s lives, and they’ll spring right back to normal now that they’re home, soothed by the cash they saved.

Dan already got some follow-up from readers:

A LOT of people have told me that the key to fixing my international iMessage issues is to just disable data roaming for my US plan and switch the Cellular Data to my travel eSIM. I literally had two different people with the same first name and last initial email me back to back. Weird. But something to give a try on my next trip, I guess.

Hilariously, there are replies to that on Mastodon that say it works, and replies that say it doesn’t.

Even checking the official Apple documentation leaves me scratching my head. It explains the mechanics of each operation you can do with an eSIM, but it’s not a “How to Travel Abroad and Tell Verizon and AT&T to Kick Rocks” document.

Like if you just want to know how you’ll get your phone calls from your US number —like in the event of an emergency or simply to when a restaurant wants to confirm a reservation— you can parse the answer from this mess:

You can make and receive phone calls with either phone number.

When you’re on a call, if the carrier for your other phone number supports Wi-Fi calling, you can answer incoming calls on your other number. When you’re on a call using a line that isn’t your designated line for cellular data, you need to turn on Allow Cellular Data Switching to receive calls from your other line. If you ignore the call and you have voicemail set up with your carrier, you’ll get a missed-call notification and the call will go to voicemail. Check with your carrier for Wi-Fi calling availability and find out whether additional fees or data usage applies from your data provider.

If you’re on a call and your other line shows No Service, either your carrier doesn’t support Wi-Fi calling or you don’t have Wi-Fi calling turned on.3 It could also mean Allow Cellular Data Switching is not turned on. When you’re on a call, an incoming call on your other phone number will go to voicemail if you set up voicemail with your carrier.4 However, you won’t get a missed-call notification from your secondary number. Call Waiting works for incoming calls on the same phone number. To avoid missing an important call, you can turn on call forwarding and forward all calls from one number to the other. Check with your carrier for availability and to find out whether additional fees apply.

(Squints.)

Anyway, the iMessage section doesn’t fill me with confidence either mostly because it relies on manual operations to move conversations back and forth between eSIM numbers, and it doesn’t answer what happens with SMS messages. The section on calls at least mentions Wi-Fi Calling, but Wi-Fi Calling is also the setting for SMS over Wi-Fi.

For example, I live in an area with poor coverage from my cellular carrier, and Wi-Fi Calling is essential. It’s also how I can send SMS messages to people that don’t have iPhones. However, if I try to send photos (MMS) it frequently craps out, but if I turn on Airplane Mode, which disables the cellular modem entirely, then the media can go through in an instant over Wi-Fi. So … what the hell happens with dual sims and SMS to my US number when I have Wi-Fi Calling turned on for a data plan abroad? Will I get the messages at all? Will I be charged that day rate fee?

This is so weirdly complicated and fussy! The documentation is murky, and the personal anecdotes can be contradictory, or might only work for certain people, with certain carriers, on certain plans.

My carrier increased the flat rate since my last trip, so I’m always on the lookout for news that dual eSIMs are now completely seamless. If Dan and Jason can’t figure it out then what hope do I have? How many technology bloggers does it take to screw in an eSIM? For now, I’ll stick with with the regrettably expensive flat rate.