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 an...