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 its latest contingency plans in the event of a no-deal Brexit.
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.