Settings > Phone > Data roaming > Always ask

Unfortunately there's not a "None" option, but you can ensure you don't click "Yes" when it asks "Allow data roaming on this connection?"

I kept getting SMS's from my base carrier that data roaming is expensive and I should be aware as to the costs, even while I was Denying all Internet access bar Wifi.

Since I switched my main carry (still roaming) over to the Droid I haven't got similar SMS's - I assume that the N900 was using data? I guess this is one of the perils of carrying what I now realise is a huge work-in-progress...any chance of us being able to point our carriers somewhere at Nokia.com to contest any charges?

Hmmm...I wouldn´t be surprised if you managed to do something like this:
- Open maps and give it permission to use gprs assisted gps location (couple of kb)
- Close it (internet connection stays open!)
- If you do not close connection it will be used as update check for app manager in background silently (check happens once in a day, ~10 mb data transfer)

At least that happened to me :|

To date I haven't actually used data on the move - only on the hotel wifi. So for example I might be using the wifi, then go out and when I wake it up it's asking me if I want to allow roaming. I always say no. I've never actually allowed data roaming on the move on the N900, ever (and this is my first time roaming with the N900 as my main phone).

Since I didn't bother to reset my data counter, I don't know how much data it's used while roaming, if indeed it did - but the fact that my carrier was sending me SMS's indicates that this is the case (especially as my Droid - which the SIM card was swapped into - is now silent in terms of such SMSs). And I'm not sure they would bother sending SMS's unless I had racked up a fairly hefty amount of data.

I guess I'm looking for as much a full explanation as to the behaviour concerning this issue, as somewhere I can point O2 to and say "It was the phone" as a basis of negotiation should I have accidentally racked up a lot more than six quid.

I used my N900 while on holiday in Italy earlier this year, and i used 0kb of data through the network.

I just changed the settings in "Settings > Internet Connections > Connect Automatically" to "WLAN". ("Always Ask" would have worked aswel, but i wanted WiFi to auto connect.)

I used the WiFi in the hotel and bars only.

I was sure that I read somewhere (before I bought the phone) that the N900 can be adjusted so that you can use roaming and not recieve charges? Does it hack something maybe? I cant remember where I read it now, but it was one of the things that I liked about the phone!

@Janniman this is not possible.

3Uk offer (and default to) ability to disable data roaming out of country

Very quick/simple regardless of country -- can be activated/deactivated through web portal.

Provides huge comfort when faced with silly roaming charges.

Interestingly my wife is using Vodafone. She has a more dumb phone (Samsung Tocco Ultra) but we still have a data package. I was surprised that voda don't offer the block. "just dont use the internet and it will be fine"

Well on that handset sure -- but on smartphone, it's far too risky. You need to intentionally break the access point definiyion to be sure (add an X to the APN or similar).

At least you learnt that cheaply (£6 - you got off lightly)

Virgin Mobile SIMs have a good solution. You can use data roaming if you need to (handy if your flights are disrupted due to a volcano), but you can't use it accidentally because you need to first send an SMS to activate it for the next 24 hours (which costs £6 and has a meagre 5MB limit).

ha i went from england to france for 2 weeks and the bill was £90 when i got home! (usually £30pm vodafone contract)
mostly from logging in here!
daylight robbery!