How to avoid international roaming iphone

Question

Hey everyone,
So I travelled to Colombia recently and in general, had my phone either turned off, or on airplane mode the entire trip. I only used it for one five minute phone call and to listen to music for about five hours accumulated. I was there for about 8 days.
I was told to put the phone on airplane mode, so as to avoid any roaming charges, as my fellow travel companions (who all also owned iPhones), said "that way nothing comes through. No wi-fi, messages, nothing".
So, yes, went with that advice.
Get home, BAM! $255 phone bill.
Now, I was obviously expecting a larger bill than normal, but I have all together $130 in roaming charges. How the eff did this happen?
Excuse me if I'm just a dummy, but I have never owned an iPhone before and this was my first time outside of North America.
I am going to Uruguay next week and obviously, don't want the same to happen.
Any advice on how to avoid this again?
Thanks in advance everyone!

Answer 1

That's not surprising. AT&T's roaming charges are $2.89 per minute, and data is $19.95 per megabyte. Text messages are $0.50 each. If you turned on the cellular without turning off cellular data, then data could have been exchanged while you were using the phone to make a call. It should be itemized on your phone bill to see where the money went. They charge a flat fee for international roaming too.
You don't need to use "airplane mode" however, to prevent the charges. "Airplane mode" disables the radios in the phone from operating entirely. However, you only get charged to for using cellular voice and data. You'll not be charged for using WiFi (at a cafe or hotel, for instance).
The phone's settings section gives you some control over this. See Settings > General > Network and note the "Cellular Data" and "Data Roaming" options. Those should be set to "Off" when you travel. If these aren't off, whenever you are out of "Airplane mode" the phone will receive notifications, look for e-mail, or whatever else you have configured that uses data semi-automatically. Because it's SO expensive (3333% what AT&T charges for domestic data), you don't want ANY data charges.
You can safely leave the cellular service turned on as you are only charged for connected calls and text messages. They are cheaper and can be avoided by not answering the phone.