Getting ready to head out on a big trip? If you’re going to be leaving the country or if you’ll be gone for more than a few days, chances are you’ll want to use your cell phone.

Know Your Network

Just about all GSM phones like those offered by AT&T and T-Mobile have the ability to work in most countries around the world. However, many smartphones on Verizon and Sprint’s CDMA networks – including most flagship Android models and the most modern iPhones – also have support for international networks built right in.

If your phone is not unlocked, your best bet is to purchase an international plan in advance from your carrier. It will still cost an arm and a leg, but not nearly as much as simply paying by the minute – or especially by the byte – when you’re roaming internationally.

For example, AT&T’s Europe Travel plan offers 80 minutes of talk time for $60 or 200 minutes for $120. This is obscenely expensive at 75¢/minute and 60¢/minute, but still a much better deal than the $1.50/minute charged to those that don’t purchase a plan up front.

The High Price of Data

For smartphone addicts, some bad news: data packs make voice plans look like a good value. $60 buys a paltry 300MB from AT&T, while $120 will net you 800MB. However, consider this an essential expense if you’re going to use data at all while roaming without a local SIM card. AT&T charges $0.0195/KB for data use while abroad.

This may sound innocuous to the uninitiated, but this is highway robbery of the worst sort. The 300MB that cost $60 up front would cost more than an unbelievable $5,900 at this rate. Downloading a 3MB picture or song would cost nearly $60, which means even spartan use of email can rack up breathtaking charges in no time. This isn’t an AT&T-only phenomenon; though rates vary, this holds generally true for the other major US carriers, as well.

Unlocking Your Phone

If your phone is locked, you can also consider simply having your phone unlocked. This will allow you to use your phone overseas using a local SIM card, allowing you to take advantage of the same pricing on voice and data that the locals pay. Verizon and Sprint will unlock your phone for use on international networks by request if your account has been in good standing for at least 60 days. AT&T will only unlock phones if you pay a fee or if your phone is off contract. T-Mobile sells phones unlocked from day one now, allowing you to use them without any further effort while traveling.

There are, however, unofficial services for unlocking, as well. iPhone users can turn to ChronicUnlocks, for example, to have their devices unlocked, whether they’re still on contract or not. This doesn’t relieve you of your contractual obligations to your carrier, of course, but will allow you to use your device with a local SIM card while abroad.

It’s best to avoid the cut-rate unlocking services out there, as they may take advantage of a jailbreak, “soft-unlock” solution that won’t permanently apply to your phone. If you upgrade to a new version of the phone’s operating system or have to restore it to factory settings, you may be stuck back at square one.

At $49.99, ChronicUnlocks is still much cheaper than paying the Early Termination Fee AT&T requires for on-contract phones to be unlocked, though Verizon and Sprint customers are normally better off simply requesting an unlock from their carrier unless their phone is brand new and ineligible.

Finding Local SIM Cards

Especially in Europe, it’s typically very simple to find SIM cards from local carriers. Voice plans are typically quite affordable – much more so than what’s offered by American carriers in their international packages – though data varies.

In the UK, for example, some excellent options exist. T-Mobile UK offers 1GB of data, 400 texts and 100 voice minutes, good for up to 30 days, for just £10.

SIM cards are often available in vending machines at the airport shortly after you arrive at your destination. Worst case, finding a convenience store after leaving the airport is a solid bet, as they’ll likely have a few options available between which you can choose.

Sizing Up SIM Cards

Though they’re hardly the size of a fingernail, a “full-size” SIM card has proven to be too big for many cutting edge smartphones in the race to make them ever thinner and pack in ever more features.

The iPhone 5 and 5S, for example, both use a Nano-SIM card, while some older models use Micro-SIM cards, which are slightly larger. These smaller SIM cards are no different technically than their larger siblings; the surface area removed is purely cosmetic. That means it’s possible to cut a SIM card down to size in order to fit into a nano-SIM slot. This Micro-SIM Cutter and this Nano-SIM Cutter can trim a full-size SIM card down to size for use in your phone, though a pair of steady hands and scissors can in theory get the job done.

Better yet is simply purchasing a Micro-SIM or Nano-SIM card in the first place, which is often possible thanks to the popularity of the devices that use them. Make sure to check what size SIM card your phone uses so you won’t purchase the wrong one!

Using Data With a Local SIM Card

For placing calls, using a local SIM card couldn’t be easier: pop it in, power up your phone, and you’re ready to start making local calls right away. Data requires jumping through one more hoop for many devices.

Most smartphones rely on an APN, or Access Point Name, in order to connect to cellular networks for data. The easiest way to accomplish this is to find a Wi-Fi connection after purchasing your SIM card and going to unlockit.co.nz from your phone. This site only works on compatible mobile devices like the iPhone, so don’t be surprised if you see a blank window on your desktop!

Tap on Create APN, select your local SIM card’s carrier and tap Create APN. You’ll then be prompted to install new APN Carrier Settings. Once installed, you should be able to use data right away. Once you return home, simply repeat this process, but select your domestic carrier.

If your phone doesn’t work with this handy site or you prefer to go the manual route, here’s a comprehensive list of international APN configurations.

Harnessing Google Voice to Phone Home

An obvious downfall of using local SIM cards while overseas is that your phone will begin using a local phone number. That might make it harder for folks at home to keep in touch with you while on the road! If that’s not your secret master plan, the happy news is there’s a great way to allow those at home to contact you at your normal number.

First, sign up for a free Google Voice account. Once you’ve done so, download the newest Google Hangouts app for iOS or Android. Though the app is named for Google’s video chat service, it was recently updated to accept incoming and outgoing Google Voice texts and voice calls.

Next, turn on call forwarding on your phone, and point incoming calls to your new Google Voice number. Even when you swap out your SIM card, this setting should remain in effect. That means calls to your normal number will be routed to the Google Hangouts app, which will alert you to incoming calls and allow you to call home without incurring expensive roaming charges.

Keep in mind that the app requires a data connection, meaning it will eat away at your international data plan if you don’t limit its use to areas with Wi-Fi. If you’d prefer, the same kind of functionality is possible with a Skype account or with many other VoIP services, but because it’s free and easy to set up, this Google Voice method is our favorite.

Have you used your phone overseas in the past? Do you have a favorite carrier to recommend in certain countries? Let us know in the comments!