Turning off all cellular data vs airplane mode

Turning off data roaming - - kills data transmission with anybody except your carrier.

Turning off cellular data - - turns off all cellular data transmission/reception and triggers the data roaming toggle off at the same time (the roaming switch actually disappears when cell data is turned off). Cellular voice remains operative.

Airplane Mode - - The switch that should have never been. It was developed in response to a since-disproven fear that phone electronics could screw up an airplane. Moving the switch shuts down all electronic transmission and reception (data and voice) making the machine nothing more than a tape player or game gizmo or word processor. To get any data/voice feature back, with airplane mode on, you must individually toggle that feature.

As far as international use - -
. leave airplane mode alone
. turn off cellular data

. You'll still have a functioning phone, wifi, gps, etc, - - but you won't have data charges. Obviously you'll have voice charges if you use the phone in cellular mode.

. If you decide you need a quick burst of data for some reason, flip it on, use it, then flip it back off. You will have accomplished your objective with one switch instead of having to reset several with the consequent potential costly sequential error.

Cellular Data Use:

As note above, the time may come when you need to use cellular data briefly. When the switch is off, data is accumulated in the far neverlands and not sent to your phone so you are not charged for it. When you flip the switch, the floodgates open and all stored crap pours in. There's a work-around. Your phone has a 'push' selection for notifications on each app. Make sure all of these are turned off prior to departure.

Email will be the biggest offender, most likely. A batch of accumulated mail, especially if it's graphics-rich, will be a big data burst. It's simple to switch your email from 'push' to 'fetch' to prevent this from happening. Remember that when you get to a wifi spot, you'll have to click the email icon to get your stuff. Nothing else is required except the initial push/fetch setup. What'll happen is that the bubble showing number of unexamined mails will not move until you tap the icon to open the app.

eracah,

Ed's reply covered all the information perfectly!

One minor point that I wanted to add is that if you're planning on using SMS (text) during your travels, you may find (as I have) that in some cases the text function won't work without internet access. Texts will appear as if they're sent, but no texts will be received until either data is switched on or Wi-Fi is available. I haven't been able to determine why that is, but I'll conduct a few more experiments this year to see if I can narrow it down.

Thanks! Very useful responses. I wondered how people used their maps without incurring data charges.
What if someone calls me and it goes to voice mail- is that a charge? ( it is an iPhone)
I'm taking a old now unlocked from AT&T iPhone 4 and buying a sim card in Germany, Italy etc as needed for local calls.

Before you leave home you can download a map app that will store all the map data on your device and work with your gps, without any data transfer on the go. There are free ones that show your position on a detailed street map (I use the DirectU apps, covers all of Europe); and pay apps with full turn-by-turn functionality.

eracah,

Regarding voice mail, you could face roaming charges even if you don't use it. You may find it helpful to read THIS short article on the subject. As stated if your phone registers on the foreign network, any calls that you don't answer will be directed back to your home voice mail and you will pay for both the incoming call and for the call to be forwarded back to your home voice mail system. The costs may be reduced if you have a travel package from your home network, but you'll have to check with them.

However, if you're using your phone with local SIM cards in Germany and Italy, the tariffs will be charged according to the network you sign up with there. You'll have to set-up different voice mail systems each time you change SIM cards. Also, when using local SIM cards, anyone from your home area that wants to call you will have to dial an international long distance call.