What you need to know when taking your mobile phone overseas

Heading overseas and using your mobile phone no longer means facing a mortgage-breaking bill on your return.

With a little advance planning, it's possible to travel widely while keeping your phone active and your data costs under control.

The first step should be to check your telco's roaming policy. The big three of Telstra, Vodafone and Optus will all gleefully put you on high-cost per-megabyte deals the moment the plane touches down. That's a bad deal unless you're desperate, but they've all got much better specific roaming plans you can hook into.

Vodafone has a roaming deal that is easily the best and simplest to understand. A flat $5 per day charge lets you access any entitlements your plan already allows in 80 countries worldwide.

Telstra and Optus have per-day packs that you pre-purchase instead. These have set allowances that are less generous, but cheaper than going on a per-megabyte deal.

If you're on a smaller carrier that hooks into one of the big networks, you'll need to check with them about roaming. Some of them provide the same deals as their network, but others block it entirely.

If you're on a prepaid mobile deal, you typically can't buy roaming packs at all, although many will allow pay-as-you-go usage at high rates.

You may also want to consider a dedicated roaming or "travel" SIM. The advantage here is that you can line it up before you travel. Global SIMs typically allow you to travel between countries with relative ease. They can be a great match if you've got multiple destinations on your journey.

If you've got the time (and the linguistic skills), the most cost-effective way to roam (at least for data purposes) is to pick up a SIM card when you land overseas.

Local SIMs typically have the largest data inclusions and while most may not make it easy to phone home from a single SIM, those local calls can be handy for booking restaurants, tourist trips or taxis.

The other big change we've seen in the roaming market is the introduction of more dual SIM phones in Australia.

Dual SIM phones let you keep your Australian SIM card in place while dropping a secondary SIM card into the phone. This means you don't have to fiddle with multiple devices or leave your local number off the hook while you travel.

There are some catches. If you got your phone through the big telcos on contract, it won't have dual SIM enabled.

We've recently seen Optus adopt a single dual SIM phone - the Huawei P30 Pro - into its lineup, but every other full dual SIM contract phone in Australia is effectively neutered for this functionality.

The exception is recent iPhones. Apple only has one SIM slot on its iPhones, but it also hides an electronic SIM (eSIM) within the newer iPhone generations.

No Australian telcos support eSIM, but plenty of international carriers do. If you're travelling with a recent iPhone, it's worth checking if it's compatible and if there's an eSIM carrier available to you.

You won't typically be able to sign up until you land, but for many carriers you can easily hook into a plan direct from your iPhone.

If you're still using the charger that came with your phone it should work across the 110/240V divide worldwide, but you will need to pack an international adaptor. If you're using a third-party replacement, check its specifications before you travel. If it won't work across worldwide voltages, you may end up with a phone ready to roam but with no capacity to charge.

Of course, if all else fails or the rest of your travel costs leave your wallet wanting, you can always disable data or call roaming on your phone and go quiet with the world for a while. But where's the fun in that?

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