Game of Thrones at 10 DogeCoin's rise Google's new Timelapse feature Apple's April 20 iPad event Stimulus check status and plus-up money Child tax credit's monthly check

I can roam the world with a Galaxy S3. So why not the U.S.?

The Galaxy S3 can be used worldwide, but apparently you can't switch between carriers in the U.S. Technically, it might be possible. Realistically, it's probably not.

Samsung Galaxy S3 Samsung

Samsung's latest flagship phone, the Samsung Galaxy S3, is about to launch in the US. I'm excited! But I'm also confused. Is this my dream phone, one that I can use with both AT&T and Verizon? Getting a straight answer has proven tough.

In the past, swapping a phone between the two major networks had been hard because they use different technologies for their 2G and 3G networks. Verizon uses CDMA (as does Sprint), while AT&T uses GSM (as does T-Mobile).

But in the full 4G world, both are using LTE, right? Sure, but they're broadcasting those signals on different parts of the radio spectrum, as CNET writer Maggie Reardon explained recently. That would seem to rule out the idea that a Verizon phone could work with AT&T.

But hold the, uh, phone. Verizon was cited by PhoneScoop as saying that a future software upgrade would allow the phone to be used globally, on the 2G and 3G networks of carriers outside the US. That means somewhere inside the Verizon phone is a GSM radio. In turn, potentially that means your phone could be used on AT&T.

Of course, even if you could do this, you'd be locked to AT&T's slower 2G and 3G speeds. AT&T "slow" 4G service and its "fast" 4G LTE service wouldn't work, because the phone doesn't have the right radio for them. Or does it? 

It's possible that all versions of the phone sold in the U.S. have radio equipment for CDMA, GSM, GSM's 3G/4G HSPA+ variant and 4G LTE. If that's the case, a Verizon phone could use AT&T's fast LTE system and vice versa, assuming the phone was unlocked and none of its transmission capabilities were somehow crippled.

Who would know? Samsung should, so I asked. Initially, I was told that the Samsung Galaxy S3 was "the same on each carrier except for the network and carrier specific services pre-loaded on the device." That sounded pretty positive. The phones all seemed to have the same basic guts inside. Samsung also said that within the U.S., no one is selling an unlocked version. You have to buy from a carrier.

I looked for tech specs at the Samsung Galaxy S3 site, but they were nowhere to be found. There are various ones online, but they don't seem to cover U.S. versions of the phone. Samsung told me specs would be posted soon.

Without them, I wanted to double-check that the phones sold by each carrier should be exactly the same hardware (given there are different versions with different internal storage options, that's already a reason doubt this). Samsung told me, "A specific carrier version of a device will not necessarily work on another carrier. You will have to check with each carrier to confirm how the service works."

That sent me off to the carriers, and here I wait. Still no word back from Verizon or AT&T on whether:

  • If you pay full-price, will the phone be unlocked for use with other carriers?
  • Will the phone work on an LTE network other than their own?
  • With Verizon, what it will take for customers to unlock their phones for use outside the U.S.? Will it work similarly to the way you unlock an iPhone 4S?

If I hear back (I'm still fairly positive I will), I'll update this column. I suspect that the phones won't work on each other's LTE networks, that they don't have the necessary radio equipment for this. I do think a Verizon phone, if enabled for global roaming, could work with AT&T's 2G & 3G networks, if you wanted and if they don't somehow block US GSM carriers.

I still want that dream phone that could fully work with either of them.

OK, most people who buy new phones seem to do it under contract, so that by the time they may want to change carriers, they may also want to just get a new phone. It might not be worth the extra expense (and power hit and space issues) to have radio equipment that's not needed.

But phones also get handed down or sold on. It seems a shame they can't go between networks more easily. Verizon's iPhone 4S, for example, has a GSM radio that allows you to use it abroad if unlocked as Verizon allows. But as this Forbes article details, it also appears to be deliberately crippled from preventing consumers from taking it to AT&T or T-Mobile within the U.S.

If people could more easily switch, whether iPhone users or Android users, it might also cause the networks to feel greater competitive pressure, which would be a good thing for consumers.

Postscript: I've now heard back from Verizon, which told me:

The Verizon model of the Galaxy S III will be global ready for GSM roaming after a software update that will be pushed sometime after launch. After the phone gets the software update to be global ready, customers don't need to call customer service to have it unlocked if they wish to use a local SIM while traveling. They can also call Verizon to have an international data plan added if they'd like.

That's nice to hear, that you won't have to call in to unlock the phone for use abroad. I'm not sure if that means, however, if a US-based SIM for AT&T or T-Mobile will work. Checking again!

Now playing: Watch this: Samsung Galaxy S III is a looker