Can I take my phone overseas? Check this before travelling

Planning an overseas jaunt? If you're taking your phone overseas - and want to avoid coming home to a huge international roaming bill - there's a relatively easy and inexpensive way to call, text and use data.

Instead of incurring roaming charges on your Australian plan, you may want to simply buy a prepaid SIM at your destination, and connect to a local mobile network. In most cases, this should be as simple as swapping out your Australian SIM card for a local one, but there are a few things you'll need to consider first:

If this sounds all too hard, don't worry - we're here to talk you through the basics.

1. Check if your phone is locked

Before you head overseas, you'll need to make sure your phone isn't locked to your provider's network. All phones sold on a postpaid plan - where you pay it off over 12, 24, or 36 months - are unlocked; however, if you purchased your phone on a prepaid plan, it may still be tied to your telco.

As a network-locked device will only work on the telco you bought it from, you'll need to get it unlocked before you can use it overseas. The most reliable way to check whether your phone is locked is by going direct to your telco (either in-store, online, or by calling tech support).

To do this, you'll need to know your phone's IMEI number. Fortunately, there's an easy, totally free way of finding it: dial * # 0 6 # (star, hash, zero, six, hash), and the number should appear onscreen. Your IMEI will be long, so be sure to write it down carefully.

Depending on which provider you're with, the steps for unlocking can vary. Below are links to unlocking guides for the four big telcos:

Unlocking your phone may incur a fee: just how much depends on how long you've had the device. Unlocks after two years are generally free, but if you request an unlock within the first six months, you may pay up to $80, depending on your telco.

Remember, if you do need help unlocking your phone, you'll need to contact the network provider from which you purchased it. So if your phone was bought on a Telstra plan, you'll need to request unlocking assistance from Telstra, even if you're no longer with the company.

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2. Will my phone work over there?

Whether or not your phone will work overseas depends on whether it uses the same network standard as used by your provider at your destination. It will also need to operate on the right frequencies.

GSM vs. CDMA technology

There are two basic global technology standards for 3G (Voice and Data) mobile phone networks. Australia uses the most popular standard called GSM. The other standard is called CDMA. Very few phones work on both GSM and CDMA, so chances are yours doesn't. Steer clear of CDMA networks, as your phone probably won't work on one.

Many countries, like Japan and the US, use a mixture of GSM and CDMA. For example, the largest provider in the US is Verizon, which uses CDMA. No GSM-only phone will be able to work on the Verizon network; even if you insert a Verizon SIM card into your device, you won't be able to call or text over a 3G network.

However, America’s second and third-largest providers, AT&T and T-Mobile, operate on GSM networks. Devices bought in Australia can work with these carriers' SIM cards, but only if they support AT&T or T-Mobile's network frequencies (more about this below) .

Since there's a lot of frequencies, and even more phones, you'll need to check if the specific frequencies (or 'bands') your phone supports include the frequencies used by your prospective carrier.

Network frequencies

Much like radio and TV stations, mobile networks operate on different bandwidth frequencies . These are measured in megahertz bands, such as 850MHz or 2100MHz.

This information is important, because your phone needs to have support for the specific frequencies on which a carrier operates. Look up the biggest carriers in the country you wish to travel to and check their network frequencies, then match them to your device by looking up its specifications - the manufacturer's website is typically a good bet.

Generally, your device’s frequencies will appear something like this in a spec sheet: “GSM 850/900/1800/2100, LTE 700/2100”. In this example, the phone would work on the GSM standard at 850MHz, 900MHz, 1800MHz, and 2100MHz. It would work on 4G LTE at 700MHz and 2100MHz.

Luckily, almost all newer devices on the Aussie market - especially big-name flagship releases, such as the iPhone or Samsung Galaxy S series - will be compatible with the majority of most-used frequencies worldwide. So it's highly likely that your phone will be fine to use on any overseas GSM network.

While 2G and 3G can be a bit tricky, 4G is a little bit easier. Almost all countries, including Australia, use a single standard for 4G called Long Term Evolution, or LTE. Your phone will still need to support the right frequencies, but you don't need to worry about technology types.

If the network you're using while overseas supports LTE, your 4G-compatible Australian phone should be able to access data without any problems. But keep in mind that if you're using a CDMA network, such as Verizon, you still won't be able to use your phone to make or receive calls or text over 3G (you can, however, use apps such as WhatsApp or iMessage to stay in touch).

And if you're looking at 5G support, 5G frequencies are most easily identified by band numbers. These have names like n78, which is the most common in Australia. Once again, you can find these in a spec sheet. You'll typically find something like this: 5G NR (Bands n1, n2, n3, n5, n7, n8, n12, n20, n25, n28, n30, n38, n40, n41, n48, n66, n77, n78, n79).

If you're travelling to the US and hoping to get 5G access, it's worth being aware that the vast majority of American 5G networks are built on a different kind of 5G to that currently available in Australia, so getting coverage may not be as simple as you think.

We've listed the frequencies that the most popular US and UK carriers' networks operate on below:

Popular US mobile carriers

Carrier	Tech	3G	4G	5G
Verizon	CDMA	850/1900	700/1700/2100	n2, n25, n25, n26, n66, n260, n261
AT&T	GSM	850/1900	700/1700/2100/2300	n5, n26, n260
T-Mobile	GSM	1900	1700/1900/2100	n41, n71, n260, n261

Popular UK mobile carriers

Carrier	Tech	3G	4G	5G
EE	GSM	2100	800/1800/2100/2600	n78
O2 UK	GSM	900/2100	800/900/1800/2100/2300	n78
Vodafone UK	GSM	900/2100	800/900/1500/1800/2600	n78
3	GSM	2100	800/1500/1800/2100	n78

3. Choose a carrier and plan before you go

After you’ve figured out if your phone will work overseas (hopefully it's a yes!), it's not a bad idea to try and work out which prepaid provider you'll go with ahead of time. We'd typically recommend going with one of the bigger providers with better coverage; it may cost a little more, but you don’t want to find yourself lost in a foreign city with no mobile coverage.

In some cases, you can even buy a prepaid SIM card through in-flight shopping on your way over. This can be a better option than waiting until you get to the airport.

Requirements for buying a prepaid SIM overseas will vary from country to country, so be sure to look this up ahead of time. In some cases, you can literally get one out of a vending machine, in others, you'll need to have your passport on hand to prove your identity.

If you're going to the US or Canada you can check out the local version of our site for that country to compare prepaid plans. If you're heading to New Zealand, we've got a comprehensive guide.

Alternatively, if you have a phone that supports eSIM, you can even buy a digital travel SIM before you land. Read our guide to travelling with eSIM here.