18 months ago, Liz changed her company’s phone account over to Three. She joined Philip Boucher-Hayes on Liveline to tell him about an unexpected bill she received recently.

Liz told Philip that she got “all the bells and whistles” when she switched. On the 10th of May this year, Liz noticed that Three had taken payment for a bill of €5,113.87 from the company account. The bill for the four staff phones was usually closer to €180 per month.

“I had palpitations. Because we’re a start-up company, we’re a small company like…my initial thing was that they’d made a mistake.”

A call to Three shed some light. It wasn’t a mistake. An employee had incurred €6471.85 worth of roaming and mobile data charges while on a trip to New York.

“I said, no. There’s no way. How could this be?”

The problem, it turns out, was international waters. Liz warned listeners to be aware that when taking a ferry, they may be charged “maritime charges”, even if the ferry stays in the EU. Her employee had managed to rack up the unusual bill on a water taxi in Brooklyn.

“If you are travelling between the UK and Ireland or anywhere on a ferry in the EU, your charges are international charges according to Three. They’re not EU charges anymore. So, if you're handing your iPad to your child and you have a data allowance, it’s not EU roaming. It’s maritime charges. Which are extortionate.”

Philip got his calculator out and calculated that if someone were to download a 90-minute film while in international waters, it would cost them €14,600.13.

Listen back to the whole discussion on Liveline here