The guarantee of free mobile phone roaming for mobiles with UK contracts throughout the EU has ended. Passengers with UK mobile phone contracts are advised to check with your phone operator to find out about any roaming charges you might get when travelling outside the EU. Likewise, EU travellers in the UK may face regular roaming charges, depending on their contract. Passengers are advised to check with the mobile phone operators for further details.
Your phone will connect to any available satellite signal when at sea unless the data roaming option is switched off, which Irish Ferries recommend. The tariffs charged are set by your own network, and not by Irish Ferries. Your network is obliged to inform you by SMS at the time your signal roams. Switch off data roaming and use WiFi onboard to avoid these charges - see further detail here: Free & Premium Wifi.