Customers will now have to pay £3.50 for each gigabyte (GB) worth of data used over a 25GB limit. The new charges, which O2 confirmed in an email to customers, will come into effect in August.
In 2017 roaming charges within the EU were abolished under new Brussels rules.
Wednesday marks the five-year anniversary of Britain’s vote to leave the EU in 2016.
O2 emailed its customers will “changes to our roaming fair usage policy” which will come into effect from August 2.
One customer received a message, seen by The Independent, which said: “As your monthly UK data allowance is over 25GB, you can still use your data in our Europe Zone.
“But it’s now subject to a Roaming Limit of 25GB.
“Once you’ve reached this limit you’ll be charged an additional cost of £3.50/GB.”
The announcement sparked fury on social media, with some arguing this is a downside of Brexit whilst others claimed it is unlikely to hit a regular family.
One Twitter user said: “Get what you vote for.”
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A second posted: “25GB limit though – that’s a fair bit of inclusive data.”
Another said: “Maybe people should spend less time staring at their phone and more time enjoying their holiday.”
The Government has introduced a maximum £45 per month limit to how much holidaymakers can be charged without explicitly opting in.
They must also be clearly informed when they’ve used 80 and 100 percent of their data.
Boris Johnson released a statement to mark the fifth anniversary of the UK’s leave vote.
He commented: “Five years ago the British people made the momentous decision to leave the European Union and take back control of our destiny.
“This Government got Brexit done and we’ve already reclaimed our money, laws, borders and waters.
“We’ve installed a new points-based system for immigration, delivered the fastest vaccine roll-out anywhere in Europe, negotiated trade deals with the EU and 68 other countries – including our first post-Brexit free trade agreement with Australia – and we’ve just begun negotiations to join the £9trillion Pacific trade area.
“Now as we recover from this pandemic, we will seize the true potential of our regained sovereignty to unite and level up our whole United Kingdom.
“With control over our regulations and subsidies, and with freeports driving new investment, we will spur innovation, jobs and renewal across every part of our country.”