What Is Data Roaming?

Roaming refers to the continued data service you get when you go outside of your mobile operator's coverage area. For example, you can continue to access the Internet or make calls when traveling internationally thanks to cooperative agreements between your cellular provider and other network operators.

Domestic roaming is usually free. Unfortunately, international roaming usually involves being charged data roaming fees that can rack up very quickly and get very costly.

You can trigger data roaming fees in several ways: by making or receiving phone calls, by sending or receiving text (SMS) messages, and/or by downloading or uploading any Internet content (such as emails or accessing web pages). Here's a brief overview of the different types of ways you can be roaming with your cellphone (wittingly or not).

You make a phone call on your handset.A friend calls you. Note: You don't actually have to answer it for you to be charged for the call. If your device is on and the call goes to voicemail, you'll be charged as an international roaming incoming call.

However, if the device is off or in flight mode and the wireless network is off and the call goes to voicemail, you won't be charged (according to AT&T). Visual Voicemail messages when roaming will be charged a roaming rate, however. Yes, this is confusing. It's probably best to put your phone in Airplane mode as I described in how to avoid data roaming charges.

You send a text message or multimedia message while abroad.You receive a text message or multimedia message while abroad.

Data roaming's the one that sneaks up on many people. We've all heard the horror stories (including this one of a guy being charged $62,000 after downloading one movie). The problem is that the price for data is usually based on the volume of data -- in kilobytes (KB) or megabytes (MB), which is hard to eyeball so you have to be vigilant about keeping an eye on your data consumption. Also, sometimes services and apps we use can keep connecting to the Internet without our knowledge, continuing to add to our bill.

Common services that would count under data roaming, if you do it over your cellphone's data card rather than a Wi-Fi network, include:

Reading, sending and receiving emailLooking up an address on Google Maps (or other online map)Doing a web searchVisiting any web pageWatching an online videoOpening an app that connects to the Internet. This one's pretty important, because you might not know it's connecting in the background. The only way to check is to go into the app's properties or permissions settings to see if it has Internet permissions (or use another app that checks that). See how to monitor your mobile data usage for some apps to help.

Rates for roaming vary depending on where you go and whether you are text messaging or voice calling. They also vary by provider. Here's an overview for the major US wireless carriers.

As of January 15, 2012, Verizon's CDMA page lists rates from $0.69 per minute for Canada, Guam, Northern Mariana Islands, and Puerto Rico to an incredible $2.89 per minute for countries like Bangladesh, Belize, Ecuador, and several others. Mexico is $0.99 per minute. Most countries are $1.99 per minute. See the full list here.

Text messaging within the US, Canada, US Virgin Islands, and Puerto Rico are at the domestic rates per your plan. Outside of these areas, $0.50 per address when sending and $0.05 per message you receive.

AT&T's roaming fees are a lot more complicated. The company offers a "World Traveler" package for $5.99 per month which gives you discounted roaming rates for many countries (but not all of them) -- so you have to check their comparison list to see if this plan is worth it for you. For example, if traveling to Denmark, you'll pay $0.99 per minute with the World Traveler package instead of the standard roaming rate of $1.39, but those going to Cook Islands have no discount. That comparison list mentioned is where you'll see the standard roaming rates.

AT&T's international roaming messaging pay-per-use rates are as follows: $0.50 per text message sent and $0.20 received; $1.30 per multimedia message sent and $0.30 received.

Finally, international pay-per-use data rates are $0.015 per kilobytes in Canada and $0.0195 per kilobytes everywhere else. Other monthly plans are available starting at $24.99 per month for $50 per MB if you're a frequent traveler.

Sprint's international roaming fees can cost as much as $4.99 per minute, although, like AT&T, you can get a package add-on (for $4.99) to get discounted calling rates while traveling, called Sprint Worldwide Voice. A $2.99 Canada Roaming add-on is available that gives you $0.20 per minute calling, saving you $0.39 off of standard roaming rates.

To find the Sprint international coverage and roaming rates, you can use this drop-down form to search by country or cruise ship or this whole list in PDF form.

Included in the list are typical GSM data rates of $0.19 per kilobyte, $0.50 per sent text message, and $0.05 per text message you receive.

T-Mobile has a similar drop-down box for finding international roaming rates by country or cruise ship. Canada is $0.59 per minute, Thailand $2.39 per minute.

For data, you get packages in MBs: 10MBs of data in Canada will run you $10; in other countries $15.

Also Known As: data roaming