Using AT&T iPhone in Europe
 

I'm going to Europe (Portugal and northern France) and am borrowing my friend's AT&T iPhone 2G that I've jailbroken and unlocked. I've got an overseas Vodaphone SIM (from Amex) to use but I only want to use wifi for data to avoid data charges on the Vodaphone account. If I set data roaming to "Off" will that do the trick? I'm concerned as I may not actually be roaming on this sim.

Thanks

Data Roaming setting only affects roaming. If you are in that Vodafone SIM's home country, you will get data. I think the only sure way is to take the SIM outwhen you're ready to use WiFi. Or maybe you can get Vodafone to disable all data on the SIM from their side.

As long as the home network is not configured to accept any access point (APN) configured (as it's the case for O2 Germany), you can avoid data connections by setting a non-existant access point.

Try airplane mode too to disable all the data services. Not sure if airplane mode on an iphone disables wifi too.

It does disable WiFi.