Going abroad? Try a local SIM for your smartphone

When traveling, why not do what the locals do? If you have the right phone, you can swap our your U.S. SIM card for a local card and save.

For $30, AT&T wants to give me a whopping 120MB of data when I'm traveling outside the U.S. Thanks, but no thanks, AT&T.

The same it true for any of the U.S. carriers, who want to charge a huge amount for their various "global" plans. Me, I go local and save.

Right now, I'm enjoying unlimited data, 300 minutes of talk time, and 3,000 text messages on my Nexus 4, as I travel through Britain. Cost? The same $30 AT&T would charge me for so little.

How'd I do it? It was easy. As soon as I exited customs at Heathrow's Terminal 3, there was my favorite vending machine in the world:

Danny Sullivan

It couldn't be easier to get going with a local SIM card than this. Pick the option you want, insert your credit card and off you go. In my case, I went with 3, a U.K. carrier that I've used years.

I actually have a SIM card with 3 that I've kept active for several years; the same is true for my wife, but the machine was handy to get my two kids going with 3's All In One 15 plan. Within a few minutes, all of our phones -- my Nexus 4 and my family on two iPhone 4s and an iPhone 4S -- were up-and-running.

Two years ago, I walked out of customs at Sydney's airport and had my choice of local phone companies with booths all designed to cater to the arriving passenger. SIM cards or even phones to rent were readily available.

Earlier this year, I went local in Germany. There, it was more complicated. There was no vending machine, but the Munich airport had an electronics store that was open. A helpful store clerk quickly got me going with

Last year, a trip to Costa Rica proved a bigger challenge. No airport machine or electronics store. Instead, I found myself in a small mobile phone shop in a beachside town. Despite me only having a few words of Spanish, and the clerk only a few of English, I ended up with a SIM card and a local plan.

Yes, there are far better things to do in Costa Rica than track down a SIM card. But for a tech lover, it's also part of the fun, getting to know how the locals deal with local carriers and the type of plans that are offered.

Downside: a different number
If you get a local SIM, you'll almost certainly save a huge amount of money versus using any global option that your local carrier offers. But it's not all perfect.

Perhaps most important to some, anyone calling or texting your US number won't reach you. If it's important that number stay active, you'll have to pass over this idea or make other arrangements.

I use Google Voice, so this isn't a problem for me. Any calls to my US number go to voice mail, which I can then access from my computer. I even have the ability to text back from my computer to whomever called, with my Google Voice number appearing.

Of course, once you have your new "local" number, you can give that out to anyone who really needs to stay in touch with you.

Will your phone work?
Another big issue is whether the phone you have will work in another country. If it's with AT&T or T-Mobile, there's an excellent chance you'll be fine, that it'll be able to transmit on the right frequencies and in the right GSM format. Don't expect you'll get 4G or 4G LTE speed, however. It's 3G that's more common outside the US.

Your phone also needs to be unlocked. I've found AT&T is very good in doing this, if you've had the phone with them long enough. With a little searching, you'll also find many companies that provide unlocking, as well as instructions on how you can do this yourself for free on phones like the Samsung Galaxy S3 or S4.

If you need an easy way to test, before you go, buy a SIM card from a rival network in the U.S. For example, if you're on AT&T, buy a T-Mobile SIM card. See if you can use that in your "unlocked" phone. If so, you're good for the trip. If not, figure out the issue before leaving.

An overlooked issue is the size of your SIM card. Full-sized SIMs are dying out (technically Mini SIMs), in favor of micro SIMs, and nano SIMs lurk out there for the iPhone 5.

Do not buy a SIM card cutter and adapter, if you can at all help it. I've tried many. They all suck. In a pinch, they do work. They also have a tendency to cause your "adapted" SIM to get stuck in the SIM slot or bend a contact pin.

Buy the right-sized SIM, if it's offered. In the end, with 3, the package included a nano SIM, meaning I had to use the included adapter to make it work with the iPhone 4. It did work, and at least I felt comfortable that a major carrier wouldn't sell something that might cause the SIM to get stuck. But I'd still have preferred the exact size.

Learning more
I wish I could provide a comprehensive guide to buying local SIMs around the world, but I can't. I hoping mainly that this column helps open people up to the possibility of going local and points them in the right direction. Airports, especially, are your first stop to look for cards and help.

See also "FAQ: Swapping SIMs to save big on calls abroad," which is an older story here on CNET with more advice that's still largely relevant, as well as "Traveling to Spain: Local prepaid SIM or international roaming?" from last year that also has some good advice.

Enjoy going local!