More than half of people fear racking up huge mobile phone bills due to data usage, with the problem particularly acute for those travelling to this year’s World Cup. The US has been named the most expensive place to use roaming data in a comprehensive survey of data usage habits while abroad.

From background data syncs to navigating unfamiliar streets, Sky Mobile’s Data Roaming Index has lifted the lid on the behaviour that’s draining our devices and the countries where it really will cost you.

Its research shows that shows that forgetting to turn off app notifications can land travellers with up to a £20 bill, while streaming just one film trailer can leave Brits up to £120 out of pocket.

Sky Mobile’s index shows that online messaging and accidentally downloading WhatsApps are the ‘data drainers’ most Brits fall foul of abroad, while using maps and navigation tools and search engines also rank highly. Booking restaurants, tours and day trips are also big reasons for Brits to turning on their data regardless of the cost.

Meanwhile a third of people admit they prioritise posting on social media enough to turn on data to do it, even though it’s likely to land them with significant charges.

Sky Mobile has created a practical guide with ‘roaming hacks’ to help people cut data usage while out of the country. Key tips include downloading maps, playlists and shows before travelling, switching on low data mode, and turning off automatic cloud syncing.

The index has been released as Sky Mobile expands its Roaming Passport Plus destinations from 55 to 120 across EU/EEA, the USA, Australia and more. Customers can use their UK data, calls and text allowances as if they were still in the UK while in one of the destinations for £2 a day, no set-up required.

Ben Case, Managing Director of Connectivity at Sky, said: “According to our research, over half of Brits are afraid to turn on roaming abroad due to potential charges.”

To view Sky Mobile’s Holiday Hack List visit here

The Top 10 Costliest Countries to Data Roam:

1. USA
2. Thailand
3. Barbados
4. Turkey
5. Egypt
6. Indonesia
7. Australia
8. Mexico
9. South Africa
10. Morocco