THE COST of using smartphones overseas will more than triple some cases this week as Telstra revealed higher prices for international data right before the holiday season.

The nation’s largest telco warned customers of the changes by text message today, announcing its redesigned “International Travel Passes” would raise the rate of excess data usage by more than 300 per cent and double the cost of global roaming in some countries.

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Customers have already flooded the comments section of the company’s online announcement to brand its redesigned plans “inadequate” and “an absolute joke”.

Telstra’s global roaming packs will hit Australians travelling to Indonesia and Thailand the hardest, where the company will charge double its previous rate.

While the two countries were previously included in Telstra’s Zone One with New Zealand, and qualified for a $150 30-day travel pass, from Thursday they will be lumped into Zone Two where the price doubles to $300.

For the price hike, they will get an extra 700MB allowance.

The cost of buying a Telstra travel pack for use in a host of countries including Canada, France, Germany, Italy, South Africa, the United States and United Kingdom will also increase by more than 60 per cent, as Telstra has moved these countries and more to a third zone.

Telstra’s Zone Three travel packs will jump from Zone Two’s $300 for 30 days to $450, with just 700MB added to their allowance.

All Telstra’s travel packs will also incur more than triple the excess data fees, as the company raises excess data rates from three cents per megabyte to 10c/MB.

There are some upsides to Telstra’s overhauled global roaming system, however, depending on where you’re travelling.

New Zealand visitors will receive more data for the same prices, with their $150 30-day pack delivering 2.2GB rather than 1.5GB, as will visitors to China, Hong Kong, Japan, Malaysia and some other countries in their $300 30-day pack.

Telstra has also added more countries to its network, including Argentina, Egypt, Finland, Mexico, and Vanuatu.

Despite the addition of new countries, Telstra customers have slammed the changes online.

One commenter employed sarcasm — “Wow. I get a whole 75MB of extra data and all I have to do is pay double when I go to Thailand” — while others branded the packs “outrageous,” “an absolute disgrace,” and “unpalatable”.

Telstra’s new data deals will compete with Vodafone’s $5 roaming deal that delivers access to a user’s monthly data allowance in 50 countries for a daily $5 charge, and services from roaming specialist firms including GlobalGig and TravelSIM.