It's definitely obvious why you're being charged £13 a month based on what is on your bill. However it seems odd that you'd be charged 'Rest of World Roaming' travelling between the UK and Norway as any cellular masts you could connect to would be on land that are in countries included in European roaming.

Hi Toby - thanks for answering.  Please can you clarify why it’s obvious I should be charged £13? I fully understand the £8, as that’s my contract, but why the additional £5?

My point is that your bill states the charge and your cap is £5 so that's why it's £13. As for why you are being charged for roaming in the first place, I wouldn't know and from the information you've given is not obvious. Someone from iD should be able to state which country you to be connecting to. Do you get any text messages from foreign networks or iD stating which network or country you are connected to when travelling to Norway?

No, I’ve never received any texts from foreign networks - I’ll try and contact iD.

What triggered my query is that I am due to go to Japan shortly and whilst I won’t need to make phone calls at all, I imagine I will be using Google maps to navigate and browsing websites for local info. As such, do you think I should stick with my existing SIM or buy a local one in Tokyo airport?

Thanks in advance! Andy

My son recently went to Japan and a local SIM is probably the best option. You can order it in advance and have it sent to you before you travel.

I always turn mobile data off on all phones when I get on a ferry. They use a satellite mobile network and that was never covered by roaming deals (before mobiles, before Brexit, and after Brexit). 

Even a text message using maritime network on the ferry is extremely expensive, even if the vessel is docked 'locally'.

One site I looked at warned :

"

****.Maritime is a satellite-based marine mobile provider and data charges will be considerably higher than your standard tariff.

If you do not disable your mobile data roaming then your mobile may automatically use this service whilst onboard. Please refer to your device's operating instructions for details on how to enable and disable these features and ensure you are aware of any data services that may be enabled and attempting to connect."

These satellite based marine mobile providers were out side any tariffs I have used travelling on ferries in the last 11 years.

I am a mobile user, and ferry user but other have no connections with either of those services providers.

I have only used  an idmobile Sim  in the U.K. or when roaming in the E.U. I am aware that Sim upgraded or contracts started after 21/6/2023 now get a maximum of 30G E.U. roaming , any contracts before that date for the E.U. are roaming like at home. I don't know how that applies to Japan.

I would also suggest in Japan get a local SIM, however I have never been there.

If your phone supports virtual Sim cards (embeded SIM or eSIM) then all you need is to scan the eSIM 3d barcode. You can use your physical SIM as normal (extra charges may apply for texts phone calls)  and (I may be corrected) but you could also use simultaneously.

one or several eSIM numbers. My kids have now all got phones that support eSIMs but I haven't upgraded yet. 

Set your phone to use the data / phone calling in Japan from the local SIM, and not use roaming.