A man was fired after racking up $23,000 in data charges whilst on holiday in Sri Lanka.

A man who was fired for a $23,000 phone bill was justifiably dismissed, the Employment Relations Authority (ERA) has ruled.

The Mighty River Power employee racked up the charges on his work phone while on a three-week holiday in Sri Lanka earlier this year.

The employee's name is suppressed.

"International roaming" charges made up $23,350 of the Spark bill, with just $6 spent on international calls and texts.

Around 1.5GB of data was used. In New Zealand, a $29 plan would cover the same data usage.

The data use was spread across a variety of apps, including iTunes, Facebook, Snapchat, Google, Amazon, Instagram, Gmail, Dropbox, and Akamai.

Analysis showed the use was consistent rather than varied - suggesting it was due to "sync" usage rather than active internet browsing.

When the employee returned to his job his boss confronted him about the charges, as well as the fact that he had returned a day later than expected, and had driven to work in a company car after only a few hours of sleep.

He was dismissed and subsequently laid a complaint with the ERA.

It was not established that the man had received a warning text from Spark after $2486 of charges had been racked up.

Spark noted the text message after Mighty River Power disputed the charges, but no proof of the text being sent could be found.

It could be established that the man was generally aware of high charges for international data usage, and that he had received texts from Spark on entry to Australia and Sri Lanka warning him of the charges.

The man also purchased a $5 sim card for his personal phone so he could make calls and texts while in the country.

Whilst the ERA ruled that his dismissal was justified, the manner of the dismissal was ruled to have been unfair.

The man was not given a fair chance to explain his bill, so the company was ordered to pay him $6000 in compensation for "loss of dignity and injury to his feelings".

The company's counterclaim, which sought orders to make the man pay the bill himself, failed.

A Spark spokeswoman said she could not comment on this specific case, but that roaming charges reflected real cash costs to Spark.

"We – like other New Zealand mobile providers - pay international carriers for our customers' access to data, minutes and voice calls on their network. We also pay 'clearing houses' who handle the billing charges for mobile carriers all over the world, and there are costs for links between NZ and overseas destinations," she said in a statement.

She said Spark were proactive in warning users about high costs and were working to bring roaming charges down.