When it comes to telephone companies, nothing irritates us more than unexpected charges for excess data usage.

This common complaint has topped the list of topics raised with the telecommunication ombudsman this year, with some users being charged with bills up to $76,000 larger than they expected. Another user was charged $571,000 for calls made after their phone was stolen on a trip to Europe and the telco argued the bill should be paid.

New data shows there were more than 14,000 complaints over excess data charges in the past financial year, with half of those for disputed amounts of $440 or more.

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Unexpected data bills are the biggest gripe of Aussie phone users, followed by disputed bills and complaints over poor contract information, a new report by the Telecommunications Industry Ombudsman (TIO) confirms.

In capital cities, telco customers are being burned by unusually high bills where the cause is not clear, and issues surrounding the adequacy of advice provided when they bought the product.

While complaints over data roaming and mobile phone coverage have significantly dropped, data disputes grew a massive 27 per cent over the past year, surpassing mobile phone coverage as the top complaint issue to the TIO.

Global roaming charges have dramatically improved. Photo: ShutterStock.

The largest complaint over excessive data charges the TIO heard this financial year was $76,000.

Ombudsman Simon Cohen says that there is a disconnect between how much data people are using and how much data they are afforded.

“The amounts in dispute are often substantial and consumers tell us they don’t understand why their usage and their charges are so high,” Mr Cohen says.

He says that research shows the average consumer is using more than two gigabyte of data a month, while the plans that people are often on provide less than one gigabyte.

“The consumer detriment evidenced in this is substantial,” Mr Cohen says.

How the telcos performed

Complaints from Telstra customers improved the least over the year, with disputes over excess Telstra data charges doubling.

There was also almost a 30 per cent increase in data complaints from Vodafone customers.

The Optus network, however, was the most improved major telco in the past year. Complaints from customers of the network were down almost 50 per cent.

Mr Cohen says that telcos were taking consumer complaints seriously.

“There’s been a number of steps that have been taken to make sure consumers are made aware when their usage is at 50 per cent, at 85 per cent and at 100 per cent of their included usage,” Mr Cohen says.

“Those reforms now apply right across the mobile telco sector, so they should hopefully have some impact.”

Confusing bills were also a major complaint. Photo: Shutterstock

“I think consumers more generally are getting more savvy about the impact of high charges,” he said.

Global roaming complaints down

While overseas data roaming charges also strike fear into the heart of most travellers, the report shows a massive 35 per cent drop in roaming complaints.

Mr Cohen says the great result is because of industry reform.

“There’ve been new rules brought in by the Australia Communication and Media Authority to make sure that consumers are told when they’re travelling overseas about the potential for high charges, and that they’re given regular information about the amount of charges that they’ve accrued,” he says.

How to beat data charges

Mr Cohen advises telco users to carefully consider the product that they’re considering purchasing to make sure that it is right for them.

“The second thing is that as they’re using the service, we encourage consumers to pay close attention to their bills and that if they’re seeing usage that they don’t understand, or they’re getting bills that they don’t think are fair, to raise those matters immediately with their service provider.”

Bill shock can also be avoided by considering smaller telco providers and paying extra for additional data packs to avoid excessive data fees.