Using Australian phones in America – very much hit and miss (smartphone)

17/02/2025
By Ray Shaw
In Consumer Advice Featured

Using Australian phones in America used to be easy. Get a local SIM at the airport. Not so much anymore, especially as 3G has ended.

This advice is general in nature. Your phone may work fine over there, but it pays to research before you go to avoid buying a ‘burner’ at the airport. It is generally applicable to most overseas destinations.

Huge Problem – bands ain’t bands any more.

The world is divided into three International Telecommunication Union (ITU) International Radio Regulations covering frequency allocations. Australia/Asia is in Region 3, the USA, South America and Greenland are in Region 1, and Africa and Europe are in Region 2 with 90 sub-regions based around geopolitical boundaries.

Put politely, the mobile phone spectrum is gold, and each Carrier fiercely protects it. To make matters worse, each carrier has a specified MHz bandwidth within each band. For example, n2 (1900) on AT&T is 5-10MHz wide, whereas Verizon is 10-15MHz wide.

US Operators and bands

	4G GSM Bands MHz	5G Sub 6GHz and mmWave
Verizon (140M users)	13 (700), 5 (850), 4/66 (1700), 2 (1900), 48 (3500)	5 (DSS 850), 2 (DSS 1900), 77 (3700), 261 (28000), 260 (39000)
T-Mobile (130M users)	71 (600), 12 (700), 5 (850), 4/66 (1700/2100), 25/2 (1900) and 41 (2500)	71 (600), 25 (1900), 66 (17700/2100), 41 (2500), 258 (26000), 260 (39000), 262 (28000)
AT&T (117.9M users)	5 (850), 12/14/17/29 (700), 2 (1900) and 30 (2300).	5 (850), 2 (DSS 1900), 66 (DSS 1700/2100), 77 (3700), 261 (28000) and 260m (39000)
Boost Mobile (7M users)	Roaming on AT&T and T-Mobile.	71 (60))< 29 (700) and 66/70 (17000/2100)
US Cellular soon T-Mobile (4.5m Users)	71 (600), 12 (700), 5 (850), 4/66 (1700), 2 (1900), 41 (2500)	71 (600), 258 (26000) and 260 (39000)

DSS means that the 4G and 5G Bands are aggregated and perform at the 4G speeds and distances.

There is another snag – CDMA (Code Division Multiple Access). It is really at 2G and 3G tech levels, but Verizon and US-Cellular widely use it in many states, and phones are carrier-locked. CDMA is cheap, and calls are cheap, which is why it is still popular. It will eventually be killed off like 3G was here.

Australian Bands for comparison

	4G GSM Bands MHz	5G Sub 6GHz and mmWave
Optus	28 (700), 3 (1800), 1 (2100), 40 (2300), 42 (3500)	40 (2300), 78 (3500), 258 (26000) and 8 (DSS LTE 1, 3)
Telstra	28 (700), 8 (900), 8 (1800), 1 (2100) and 7 (2600)	78 (3500), 258 (26000) and DSS with LTE 5, 7, 26
Vodafone (now collaborating with Optus, so this is its frequencies)	5 (850), 3 (1800) and 1 (2100)	28 (700), 78 (3500)258 (26000)

The only US/AU common 4G Band is 5 (850), used by Vodafone AU, T-Mobile, and AT&T.

There are no common US/AU 5G bands.

CyberShack always lists 4G and 5G bands in its reviews, but the chance that a phone bought here will work in the US is slim. Your best bets are the Samsung Galaxy S23/24/24 series (Qualcomm Snapdragon versions only) and Google Pixel 7/8/9 series (See Roaming later).

IMEI/VoLTE issues

With the introduction of 5G, it has become mandatory in the US and AU for phone makers to certify each model of their phones on local networks. This is not cheap, which is why the Telcos sell most phones in the USA.

VoLTE (Voice over LTE) makes a 5G phone call, and its use is carrier-dependent as it uses different control signals for each carrier.

A requirement is that the unique IMEI numbers of all certified phones are downloaded to the local Telco, and when a ‘foreign’ 5G phone tries to connect, it is rejected as not certified.

This was not the case for 4G GSM and 3G UMTS (Universal Mobile Telecommunications Service) phones.

In Australia, a 5G phone purchased overseas with compatible Australian bands may work here if it is first activated on the overseas network. Grey market Xiaomi/Redmi/Poco had huge issues with the 3G shutdown and not having Australian-registered IMEI numbers.

Wi-Fi 5GHz and 6GHz bands are different too

In brief, US Wi-Fi 6 and 6GHz bands are different. Grey market equipment (not bought from legitimate Telcos) can interfere with other uses of the 5 and 6GHz bands. A phone can be confiscated with significant fines.

This could prevent you from using Wi-Fi calling, as US routers may only connect to the 2.4GHz network.

Telstra, Optus and Vodafone roaming may be the safest

The main Australian carriers have roaming. All warn that roaming depends on being in the range of a compatible local carrier.

Telstra: $10 per day 4G roaming service for the USA and many other countries. It also has a list (out-of-date) of eligible Apple, Samsung, OPPO, Google Pixel and Motorola phones.

Optus has a similar $10 per day plan

Vodafone has a $5 per day plan with lower data allowances.

CyberShack’s view: Using Australian phones in America is risky

Using Australian-certified phones anywhere overseas is becoming a big risk, too.

At best, you may get some 4G and no 5G. Switch 5G reception off.

Buy a local physical 4G GSM SIM at a US Airport only after asking if it will work in the states you want to visit. If it is not AT&T or T-Mobile, forget it.

Europe is not quite as risky, but 4G is the best you can hope to get.

If you want to check for the US, enter your IMEI here. We tried the latest Samsung S25 Ultra, and it can use 4G bands 2 (1900), 5 (850), 4/66 (1700/2100), and 12 (700) with 4G VoLTE compatibility. It cannot use an eSIM or 5G.

You can see why US frequencies are gold. The aqua blue represents mobile phone use.