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Cellphone Roaming in Southeast Asia

How to Stay Connected via Phone or Data While Traveling in Southeast Asia

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Smartphone surfing in Changi Airport, Singapore

With a GSM phone, you'll never go without a phone connection in places like Changi Airport in Singapore.

Image © Getty Images

Travelers to Southeast Asia, take heart: under a few circumstances, you don't have to leave home without your phone. Cellphone roaming in Southeast Asia isn't just possible, it's very easy to do! Certain U.S. cellular phones will work in Southeast Asia, so if your phone meets a few conditions, you'll be able to call home on your own handset to tell the folks how you're handling your Vietnam itinerary, or check into Foursquare while viewing the Singapore Skyline from the Marina Bay Sands SkyPark.

The region's major cities and tourist spots are mostly covered by each country's cellular providers. Southeast Asia's mobile penetration rate ranks among the highest in the world.

Smartphones are commonplace in digital economies like Singapore, Brunei and Malaysia. While Internet penetration is relatively low in countries like the Philippines, Indonesia, Thailand and Vietnam, advanced mobile Internet networks are thriving in these countries' urban centers. (source) The closer you are to the cities, the greater your chances of getting a signal.

There is a catch - several of them, in fact. You'll be able to use your phone only if:

  • Your phone uses the GSM cellular standard;
  • Your phone can access the 900/1800 band; and
  • Your phone's SIM can access the local networks - which means that
    • Your provider allows international roaming; or
    • Your phone is SIM-unlocked, allowing you to use prepaid SIM cards

Does Your Phone Use the GSM Cellular Standard?

Not all cellphone providers are created equal: in the U.S., digital cellular networks are split between GSM and CDMA. (Consult this About.com page for more information about the difference between the two standards.)

U.S. operators using the GSM standard include AT&T (formerly Cingular) and T-Mobile. Verizon Wireless and Sprint use the incompatible CDMA network. CDMA-compatible phones won't be much use in a GSM-compatible country.

Can Your GSM Phone Access the 900/1800 Band?

Outside the U.S., Japan, and Korea, the world's cellular phones use GSM technology. However, the U.S.'s GSM networks use different frequencies than the rest of the world: In the United States and Canada, GSM cellphones use the 850/1900 band - providers everywhere else use the 900/1800 band.

That means a dual-band GSM phone that works perfectly in Sacramento will be a brick in Singapore. If you have a quad-band phone, that's another story: quad-band GSM phones work equally well on 850/1900 and 900/1800 bands. European phones use the same GSM bands as those in Southeast Asia, so no problem there, either.

Once you have both issues settled, let's move on to your choices: using your current plan to roam internationally, or buying a prepaid SIM at your destination.

Is Your GSM Phone Locked to a Single Cellular Provider?

Even if you have a GSM phone that can access the 900/1800 band, your cellphone may not always play well with local networks. You have to check with your carrier if your contract allows you roam internationally, or if your phone is unlocked for the use of other carriers' SIM cards.

The SIM (Subscriber Identity Module) card is unique to GSM phones, a transferable "smart card" that holds your phone settings and authorizes your phone to access the local network. The card can be switched from one phone to another: the phone simply assumes the new SIM card's identity, phone number and all.

GSM phones are often "locked" to one cellphone provider, meaning they cannot be used with SIM cards other than the SIM card they originally came with. Having an unlocked phone is important if you want to use it with prepaid SIM cards from the country you're visiting.

SIM-Locked Phones and Roaming With Your Current Plan: Does your plan allow International roaming? Check with your phone operator if you can use your phone in Southeast Asia, and what services you can use while you're roaming. If you're a T-Mobile user, you can read T-Mobile's International Roaming Overview. If your phone uses AT&T's network, you can find the info you need at their Roaming Packages page.

Be warned: it will cost you a lot more to make or receive phone calls while roaming abroad, to say nothing of using your iPhone to check into Facebook from overseas. Beware of push email and other apps tapping the Internet in the background; these can tack a few extra zeroes on your bill before you know it!

PROS: Use your own cellphone and get billed on the same account you use at home
CONS: Expensive, limited coverage; if you're browsing the Internet while roaming, you can rack up those data roaming fees pretty quick

More information on data roaming (and how to avoid it like the plague) can be found in the following articles:

SIM- Unlocked Phones and Buying a Prepaid SIM Card: If you have a quad-band GSM phone, but you think you're being stiffed by your provider on your roaming fees, you might also consider buying a prepaid SIM card in your destination country.

Prepaid SIM cards can be bought in every Southeast Asian country with GSM cellular service: simply buy a SIM pack, insert the SIM card into your phone (assuming it's unlocked - more on that later), and you're ready to go.

Prepaid SIM cards have a "load", or balance, included in the package. This balance is deducted as you make calls on the new SIM; the deductions depend on the rates included with the SIM card you purchased. You can "reload" or "top up" your balance with scratch cards from the SIM card's own brand, which can usually be found at certain convenience stores or sidewalk stalls.

Before you can use a local SIM card, though, you have to check if your phone is "locked" with your current provider. Service providers often "lock" handsets, permitting only their SIM cards to use the phone. This is done to prevent users from transferring their subsidized handsets to competing carriers. However, if you're a longtime subscriber, your carrier might provide an unlock code if you ask nicely enough.

Check with the SIM card provider's homepage for each card's available services and call costs:

PROS: Pay local rates for calls, saving up to 80%; low-cost Internet surfing for 3G-capable networks
CONS: You'll use a different cellphone number; some instructions only available in local language

For details on individual prepaid cellular providers in Southeast Asia, read our articles here:

  1. About.com
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  3. Southeast Asia Travel
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  5. Cellphone Roaming in Southeast Asia

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