More Mobile: Getting Started with Dual SIMs (Premium)

Back in the early 2000s, my wife and I started traveling internationally again, first as a couple and then with the kids each year. One of the big problems was connectivity: our cellphones wouldn’t work in Europe unless we spent a lot of money and, even then, data was out of the question. I recall driving into East Boston ahead of a May 2003 trip to Germany to pick up a rental Nokia handset that we could use overseas to check in on our kids while we were away; they were staying with different grandparents. To find the place with the rental phone, I had printed out directions from MapQuest on paper. It was a different era.

A year or two later, my wife gave me a similar European-compatible candy bar-shared phone so that we would have a phone in Europe, the idea being that we’d pick up a local SIM card wherever we were traveling and just use that for the duration.

I also recall bringing the first iPhone to Europe the summer it was released in 2007. Back then, the iPhone didn’t even have a roaming toggle let alone any sense of international roaming. And I had already heard stories of people receiving foot-tall stacks of paper bills from AT&T upon their return from an overseas trip, and them owning the firm thousands of dollars because they used their iPhones while away. I was afraid to even turn the thing on, but I mostly just left it in Airplane mode and tried to use the city-wide Wi-Fi that Paris had just then installed around the city.

A few years later, I was among the first, if not the first, to travel from the U.S. to Europe with a prototype Samsung Windows Phone 7 handset about two months before the then-new platform launched. I wrote an article about my experiences called “An American Windows Phone in Paris.”

Over time, of course, connectivity got better and American carriers slowly lowered their international calling, texting, and data prices while upping the amount of data one could even purchase. The first few years I did use AT&T data in Europe, for example, I could purchase 800 MB of data at great expense during a month … and that was it. There was no way to add more or get that amount again.

To get around this problem, we would often purchase a local SIM from a wireless carrier in whatever country we visited. We did this in France and Spain multiple times, as I recall, and at least once in Germany. In each case, we could purchase a lot of data (for the time, like 1 GB) for very little money ($30 was the going rate for a while there as I recall). And we could always easily re-up it as needed.

That was fantastic, but there were still hurdles. To use an international SIM in a U.S.-based smartphone, the phone had to be unlocked by the carrier. And in the early 2000s, this was unusual, with carriers often keeping users’ handsets locked so that they could not switch carriers.

And even if you had an unlocked phone, you could only keep one SIM in it—and thus access only one cellular network and use one phone number—at a time. So when I used an international SIM, I lost my home phone number, meaning I’d miss phone calls, text messages, and voicemails until I swapped that SIM back in.

Adding to the drama, SIM cards were slowly becoming smaller over time, so I had to keep little packets of SIM adapter cards so I could use a smaller SIM card in a phone with a larger SIM slot. But whatever. Slow/some data is always better than no data, and it was fascinating to watch the cellular situation evolve from untenable in the beginning to almost completely seamless during this 20-year period.

And when Google introduced its Project Fi plan—later called Google Fi—providing, among other things, the same low, transparent pricing for data overseas as you paid in the United States, I signed right up and tested it on various trips to Europe, always swapping out my AT&T SIM—I’d kept the same phone number since I switched from Verizon in 2007 to get the first iPhone—for the Google Fi SIM before leaving.

This was, of course, tedious. So in 2015, I finally switched to Google Fi, porting over my number from AT&T. Today, I’m using Mint Mobile, which basically has no useful international coverage at all, because it’s a lot less expensive than Google Fi, and I made that change at the start of the pandemic knowing that I wouldn’t be traveling internationally for a while anyway.

But with COVID restrictions easing this past summer, finally, we traveled to Mexico twice, in June and August, and so I started a new, secondary Google Fi account with a new phone number to use on these trips. One of the many nice things about Google Fi is that you can pause the account for several months at a time and not pay for the service while it’s paused. So I’ve been pausing the account between trips and, as I write this, I’ve just activated it again for our next trip, also to Mexico, this coming week.

What’s changed between my early Google Fi usage and now, of course, is the emergence of smartphones equipped with dual SIMs. Most modern smartphones now support this capability, which lets you call and text with two phone numbers while accessing one cellular data network; when I travel overseas, I still have access to my normal phone number, but I can simultaneously access cellular data over Google Fi.

When this functionality was first introduced, it took the form of large SIM trays in phones that could support two physical SIM cards. But in more recent years, the more typical configuration is one SIM card slot/tray and one eSIM (for embedded SIM). And there’s little doubt that we’re moving to an all-eSIM future soon. Which makes lots of sense, as eSIMs have several key advantages over physical SIM cards.

The most obvious, of course, is that you don’t need to fiddle with a tiny SIM card. The night before one trip to Amsterdam several winters ago, I was switching to the Google Fi SIM in my Nexus 6P when it fell into the couch and then proceeded to fall further so that it was actually inside of the couch. I had to cut open the wood bottom of the couch with a saw to get it back.

eSIMs have many other advantages, of course. For example, they can store multiple carrier profiles so that you can switch between two or more accounts on the fly at any time. The convenience here is staggering, especially when I think back to how different things were when I was using printed directions to find a place in East Boston about 20 years ago.

Despite my long history of international travel, I don’t have a lot of experience with dual SIMs. Part of the reason is just a coincidence of timing: I switched to Google Fi when dual SIMs were just becoming the norm and so I didn’t need to deal with that; my SIM worked great in the U.S. and abroad.

But now that we’re traveling again and I’ve switched to Mint Mobile, I’ve started to experiment with dual SIMs. And depending on how the world goes this coming year, I’ll either keep doing that or switch back to Google Fi. We’ll see.

When we traveled to Mexico in June 2020, I put the Google Fi SIM in a Huawei P30 Pro for photo-taking out in the world and I kept my Google Fi SIM in my Google Pixel 4a with 5G; I disabled cellular data on the Pixel so I wouldn’t get any weird charges. But when we went back to Mexico in August, I went the dual-SIM route, this time via my wife’s Samsung Note, and after experimenting with it on my Pixel 4a with 5G. That worked well, so I went the dual-SIM route again for our October trip to Paris, this time with my Pixel 5a. I’ll be doing similarly for our trip next week.

This time, of course, I’m using an iPhone. The process is similar to that on Android, thankfully. And even better in some ways, as the iPhone 13 Pro I purchased supports two different dual SIM configurations. You can have two eSIM-based accounts active at the same time, or one eSIM and one physical SIM. And as with Android, you can configure the eSIM(s) for multiple accounts, activating the one(s) you want on the fly. So that’s nice.

To get started, I first researched whether Mint Mobile and/or Google Fi supported eSIM on the iPhone, and both do. Since the Mint Mobile SIM was already in the iPhone, I decided to add Google Fi via eSIM using Google’s quick setup instructions. Basically, I resumed my Fi service (which has been paused since August), installed the Google Fi app on my iPhone, and then opened iPhone Settings and navigated to Cellular > Add Cellular Plan. That triggered a QR code scan from the Google Fi website, and the iPhone told me that “a cellular plan from ‘Carrier’” was ready to be added.

At that point, I was prompted to add labels to the two SIMs, one of which is my Primary SIM and the other is my Secondary SIM. So I renamed them to Mint Mobile and Google Fi, respectively.

Next, I had to configure which would be the default line, which Apple describes as “the line used to call or send messages to people who are not in your contacts.” (The people who are contacts can be assigned to a preferred line, which is fine. But I’d rather have a global toggle for that.) Anyway, I choose Mint Mobile as the primary line.

Next was a similar choice for iMessage and Facetime. Here, again, I chose Mint Mobile since that phone number is associated with these services.

Finally, I had to configure which to use for cellular data. As noted upfront, you can perform calls and text messages with both accounts at the same time, but you can typically only use one data network and toggle between them at any time. (Oddly, there’s an option on iPhone that lets you use both data networks at the same time. But I left that disabled since I don’t want Mint Mobile to access data in Mexico.) I chose Google Fi as the cellular data option just to test it, but I then put it back to Mint Mobile, where it will stay until we fly.

Looking over the Google Fi settings in the iPhone, I made two changes. The phone number hadn’t been filled in automatically for whatever reason, so I configured that. And I turned Data Roaming on. (As it turns out, these might have been unnecessary because of what I did next…)

After that, I opened the Google Fi app and stepped through the short setup process. The key bit here is to activate Google Fi on that device and make a few manual configuration changes so that calls and texts work properly. Then I rebooted the iPhone, tested that Fi-based data connectivity worked, and then switched data temporarily back to Mint Mobile. I exchanged phone calls and texts with my wife on both lines as well. All is well.

We’re leaving for Mexico next Thursday assuming there isn’t some COVID-related snafu. So I’ll write about my experiences with the dual SIM configuration during or after that trip.