Reality Check: Does the EU mean cheaper roaming charges?
The claim: British holidaymakers would have to pay more to use their phones abroad if we left the European Union.
Reality Check verdict: It's fair for the EU to take credit for the abolition of roaming charges next year, but we can't say that if the UK left the EU that British consumers wouldn't still benefit from the deal, or that prices would go up.
When you travel to a foreign country with your mobile phone, you are roaming.
Roaming charges are added by mobile operators for calls, texts and internet browsing when phone users are abroad.
An EU regulation will abolish roaming charges in EU member states from 2017.
Decreasing roaming charges is something that the European Commission has been working on for about a decade.
Without the EU's institutions, it would have been very difficult to bring countries together to impose this, and the mobile telecoms companies themselves certainly didn't have much interest in it.
"The UK led the charge," boasts a press release from Downing Street on Wednesday.
But it's difficult for any single country to take the credit for the roaming measures, which were a joint initiative.
As a member of the European Economic Area (EEA), Norway is part of the deal, but Switzerland is not, according to this answer to a European parliamentary question by the commission.
If Britain votes to leave the EU, it's not a foregone conclusion that it will benefit from the EU deal to scrap roaming charges - but there could still be a deal to abolish them for Britons. And operators are free to lift tariffs.