I seem to be on a travel theme today.
From June 2017, there will be no roaming charge for using your mobile phone in other EU countries. Is the EU great or what? It is good but the deal is wider than that. Non-EU countries in the European Economic Area are also covered by these rules, so if the UK joined the EEA or just negotiated to keep the system in place, roaming charges might not be affected. Anyway it is not correct to imply that this benefit is definitely dependent on our staying in the EU.
I don’t care either way but that’s cos I’m an old fart and never use my phone when I’m on holiday, I’m trying to get away from it all. But I realise that it’s important to you young cyborgs and business people who travel:)