ALMOST nine in 10 Australians rely on a smartphone for everything from works calls to personal banking, navigation and photography.

But just when smartphones are at their most useful — when you’re in a foreign location — using them to their full potential can become much more expensive.

Despite regulatory changes, global roaming is still one of the biggest bill-shock risks in using a mobile phone, stinging almost half a million Australians over the past two years, according to a Finder.com.au study.

And experts warn the situation could worsen for some users after Telstra quietly rolled out a new roaming scheme with daily data limits this month, even though some of its biggest competitors are introducing cheaper alternatives.

Telstra’s new plan removed its three, seven, 14 and 30-day International Travel Pass packages, replacing them with one $10 International Day Pass for use overseas that includes calls and SMS messages to overseas numbers, and 100 megabytes of data use.

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Telstra consumer postpaid director Kevin Teoh says the new plan is “part of our ongoing effort to make staying in touch when overseas easier” and 100MB is more than the allowance offered in larger packages before.

“With the new Day Pass, customers will only be charged for the days they use their mobile overseas and will have more data to use when accessing helpful travel services like maps, translation and social apps,” he says.

But Foad Fadaghi, managing director of technology consultancy firm Telsyte, says the new passes are restrictive for data users because daily allowances do not roll over to the next day.

“They’re doing it to generate more revenue,” Fadaghi says. “This is going to be more difficult than the previous approach for some people. It’s going to make them monitor what they use daily.

“You don’t want to be spending your whole day overseas making sure you don’t go past your limit.”

Travellers using Telstra’s International Day Pass who download more than 100MB in a day will be automatically charged 3¢ per megabyte, unless they purchase an additional $25 pack that delivers one gigabyte of downloads over 31 days.

Telsyte research shows many Australians have already rejected buying travel passes from their carrier, however, as only 23 per cent of consumers prefer to pay for the convenience of keeping their mobile phone number overseas, while 32 per cent would rather buy a SIM card at their destination, and 24 per cent rely on wi-fi hot spots alone.

Previous bill shock could be behind their reluctance. A Finder.com.au survey found 400,000 Australians have been stung by a big mobile bill after an overseas holiday in the past two years, with women accidentally spending an extra $317 and men $233 on average.

Finder.com.au telco expert Alex Kidman says “apps running in the background” as well as “automatic updates and video streaming” can easily consume more data than users expect, and could lead to a nasty surprise upon their homecoming.

Consumers should receive regular warnings about phone use overseas, though, under regulations introduced in 2013.

The Australian Communication and Media Authority’s International Roaming Standard dictates that you must receive an SMS alert when you turn on your smartphone overseas, and Optus, Telstra and Vodafone must also detail what it would cost to use services in your location.

Carriers must also provide warnings at $100 increments, or when you’ve used 50, 85 and 100 per cent of your international roaming allowance.