The government has warned that if there is a no-deal Brexit “surcharge-free roaming when you travel to the EU could no longer be guaranteed.”
This is because the EU directive which capped the prices mobile phone operators could charge each other will no longer apply to the UK after Brexit.
But Brexit Secretary Dominic Raab told the BBC that two mobile operators had agreed to keep free data roaming.
And the government is proposing to cap any data charges at £45 a month.
The document says that “in the unlikely event” of the UK leaving the EU without a deal, consumers should “check the roaming policies of your mobile operator before you go abroad”.
The government has published contingency plans for driving licences and passports and phone charges in the event of a no-deal Brexit.
The plans say anyone travelling to the EU after Brexit should make sure they have at least six months left on their passport, although that will not apply to travel to Ireland.
People applying for a new passport after Brexit will continue to get burgundy passports for a while – although they will not say “European Union” on the front cover, the plans say.
Blue passports will start being issued from late 2019.
Extra charges for people using their phones in another EU country were scrapped in June 2017. But the EU regulation banning them will not automatically be part of UK law after Brexit on 29 March next year.
In theory this means UK mobile operators, if they want to, could reintroduce the charges that could make it expensive to use a mobile phone in another EU country.
However, the government said it would legislate to make operators set a cap of £45 a month on data usage while abroad – in line with the current EU limit of €50.
Mr Raab told BBC Radio 4’s Today programme two mobile operators, Vodafone and Three, had publicly agreed not to bring back roaming charges for British citizens.
The cabinet met earlier for a three-hour no-deal planning session, which included a presentation by Bank of England Governor Mark Carney.
Mr Raab said the government was aiming to get a Brexit deal with Brussels by mid-November at the latest but was stepping up contingency planning in case that did not happen.
He said one of the consequences of a “no deal” Brexit “is that obviously we wouldn’t pay out the money that has been agreed as part of the withdrawal agreement”.
The UK would “recognise our strict legal obligations” but that the amount paid would be “significantly, substantially lower” than the £39bn agreed with the EU.
He insisted this was not a “threat” to the EU but a “statement of fact”.
Will there be roaming charges?
By Rory Cellan-Jones, BBC Technology Correspondent
“Put back those roaming charges we’ve just scrapped? We wouldn’t dream of it!”
That’s the public message coming from the UK mobile phone operators about the threat of higher costs for travellers from a no-deal Brexit. But off the record there is a subtler message – it all depends on what our continental colleagues do.
Roaming may be free for customers but not for the operators. Every time you use your phone abroad your home operator is charged a fee by the one you are using abroad. That rate has been capped by the EU as part of the abolition of roaming but once the UK leaves all bets are off.
“If we leave the market they wouldn’t be bound by the directive,” says one operator. “They could treat our customers like someone from America or Australia and double or triple the charge.”
Business leaders have repeatedly warned about the consequences of leaving the EU without a deal, with the CBI saying the UK would face tariffs on 90% of its EU exports and a number of new regulatory hurdles.
UK consumers could find going on holiday and making card payments for EU products more expensive because Britain would no longer be part of the EU’s payments process.
There are also concerns about delays at the UK border.
The Road Haulage Association has warned it will take “an average of about 45 minutes to process one truck on both sides of the channel” if customs checks are put in place.
“If that happens then the queues of HGVs in Kent will make the jams seen in the summer of 2015 appear as little more than waiting for the traffic lights to change,” it adds.
Mr Raab said there was a risk of disruption at the border if the EU did not respond “with the collaborative spirit” he said the UK “would want to show”.
The UK government was planning contra-flow systems on the M20 and was talking to EU member states about “mitigating” potential disruption.
And he took a swipe at businesses, such as John Lewis, saying: “I think it’s probably rather easy at this moment in time for any business that isn’t doing rather well to point to Brexit.”
“I don’t doubt that some of the uncertainty around these negotiations will have an impact on business, that’s why we are putting all our energy into getting the good deal we want with our EU friends and partners.
“All I am just gently saying is that it’s rather easy for a business to blame Brexit and the politicians rather than take responsibility for their own situation.”
Labour MP and chairman of the Commons Brexit Committee Hilary Benn said the government should be concentrating on trying to get a deal, as leaving without one would be “the worst possible outcome”.
“The focus on no-deal is, in part, about trying to handle the open warfare that has affected the Conservative Party when it comes to Brexit,” he told BBC News.
Last month the government published 24 no-deal documents covering industries including medicine, finance and farming. There were warnings of extra paperwork at borders and extra credit card charges for Britons visiting the EU.
Writing in the Daily Telegraph, Mr Raab said Thursday’s 28 documents “range from protecting consumers from mobile phone roaming charges to upholding environmental standards”.
More no-deal publications are expected in the coming weeks.
Labour MP Ian Murray, a member of the campaign for another referendum, said: “Nobody voted to make Britain poorer, to diminish our national influence or to ruin their holidays.
“The government has no mandate for any of this and it’s too big an issue to be left to a Brexit elite in Westminster. That is why we must have a people’s vote on the final Brexit deal.”