I'm more interested in a SIM that can roam in multiple countries. The Vodafone Spain SIM sounds interesting as you can roam in multiple countries. I don't know about UK SIMs.

It can roam in the EU, the UK, Switzerland, the US.

Probably also nearby Middle East and Africa too.

But the roaming data allotment is like a fraction of the amount of data you could use in Spain, so for instance, you might get 80 GB for 20 Euros to use in Spain but the amount of data you can roam with outside of Spain is 20 GB or less.

Not according to Vodaphone ES.

The UK SIM is a single UK SIM from 3. I bought it from a vending machine at LHR Terminal 3 in January 2020. Coincidentally, I've been using LHR as as a European entry point since then, so I've been able to top up. If I lose that number, it's not a big deal.

I am on the original Simple Choice plan due to a promotional add on that I would lose by changing plans, so I don't get high speed T-Mobile data when roaming internationally (even in Canada and Mexico) except the 5 GB for T-Mobile locations. I have international stateside calling for $10/month across all lines on my account. It's normally $15/line per month.

As for Australia and Taiwan, Mrs. Majuki's sister is in Sydney, and we typically make the trip there once per year. It's handy for friends and family to have the same number. With timed reloads, I only burn A$10/year, if that. (Some years I have made two trips.)

The in-laws, my engineering colleagues, and some customers are Taiwan based. They all have my Taiwan Mobile number. To maintain that number and the prepaid balance, there just has to be activity once every 6 months. Like with Australia, I can time activation of a data package with our annual end of year trip. During the summer, I activate a 1-hour data package for NT$30. Even without a trip there, such as for 3 years during the pandemic, US$2/year was worth it to maintain the service. Coincidentally, both Mrs. Majuki and I switched our Taiwan Mobile service to eSIMs in January this year.

Our trips tend to be longer in duration, so having local SIMs makes sense. Furthermore, T-Mobile frowns on roaming for extended periods of time. Our post-pandemic trip to Sydney last year spanned 3 billing cycles. Roaming for that trip would have earned each of us a strike having roamed 100% for one billing cycle.

Low data mode pauses automatic updates and background tasks. Low data mode can be turned on for cellular data and/or WiFi data.

And if you pick the right carrier and turn on wifi calling, they can even call you on it when you're not in Australia!

Unfortunately Optus isn't the right carrier. They limit Wifi calling to Australia. (Yes, it's actually geo-blocked at the network level! Go figure!)

Are Australian plans any good? Good roaming ability?

I have a stupid question - I see this kind of answered on the Internet but still don't quite understand it.

iPhone with US SIM with Wifi Calling enabled + data eSIM.

Goal: not accidentally use the US SIM when overseas for either data and call/text.

I know I can turn off Data on the US SIM. However, what I don't understand is how to make the call / text portion to only stay on Wifi calling (or data via eSIM). I end up disabling the line since that would be the safest. However, that means no Wifi Calling/Testing unless I am on Wifi and disable cellular completely.

Is there a way to keep the line on and not have it going to cellular at all? I don't see an option to disable roaming for voice/text. Googling shows:

https://support.apple.com/en-ca/HT201299
Turn Voice Roaming on or off: With CDMA networks, you can turn off Voice Roaming to avoid charges from using other carriers' networks.

Thanks.

if you aren't on AT&T, use the network selection screen on the US-sim to connect to some network that doesn't have a roaming agreement... so your US-sim will always connect to that "bad" network (no connection) and wont incur any charges

won't work ifyour US-sim has roaming agreements on all the current networsk, or AT&T(which disables the network selection screen)

Does your carrier allow you to turn off roaming? If so, you can do that. Wifi calling will still work.

I use a pre-paid provider in the US, and whilst they do allow roaming, you have to put credit into your account for it to work, so I simply don't do that. No roaming means no accidental roaming!

Australian prepaid mobile plans are relatively cheap now days, however they are not good for roaming. They either don't support it, or if they do it's generally expensive enough to make it not worth doing.

Besides turning off the Data Roaming option on that line, and the other suggestions here, you could contact your carrier - T-Mobile for instance has an option, per line, to block all roaming charges so one can't accidentally enable something while traveling.

So they're only good for use within the country? What's a good plan like? I think I might be better off sticking with T-Mobile.

Correct. For example, Optus prepaid currently has a 50GB/28 day plan for A$15 (US$10) for the first month, with an eSIM option. Vodafone has the same although I'm not sure if they do eSIMs. Need more data? Vodafone will do 600GB/28 days for A$65 (US$44). Both have stores in the arrivals area at major Australian International airports (although not necessarily with these plans). None of those plans will have roaming.

Thanks everyone. I have AT&T - I guess that explains why there was no option to select a roaming network.

I guess I will just be careful - disable the line completely when I leave Wifi and turn on my data eSIM.

Thanks,

Would tunneling Wi-Fi calling via an Australia based server be a workaround? Mrs. Majuki uses Skype to call her sister, so there's not a real need to try this. I have received texts via Wi-Fi calling with my 3 UK SIM. I haven't tried with Taiwan Mobile.

Yes, and the decision reverts to the duration of the trip and quantity of data needed. If my plan included 5 GB of high speed international data per month, I'd be far less inclined to activate an eSIM prior to traveling.