I am going to Spain for 3 weeks and I want to use my Iphone as an ipod/gaming device on the plane. If i keep the phone off the whole time while I am overseas is there any chance of me having extra charges?
If you have a WIFI connection you can keep it in Airplane mode like jmann said but turn WIFI on and you will be able to access email, app store and anything else that uses data. There will not be any charges to your account.
There may be charges to connect to the WIFI though. That just depends on who run the WIFI spot.
My wife traveled to Belgium a few weeks ago and before she did I called AT&T about this. They said if someone called and left her a voicemail and her phone was ON she would be charged even if she didn't listen to it. I even asked about if she still would if it were in Airplane mode and she said yes. I don't understand it but that is what I was told.
If the phone is on and you receive a call (it actually rings) you will be charged whether there is a voice mail or not. The charges start when the call reaches your phone. If your phone is in airplane mode the call never reaches your phone and you will not be charged.
If spend 9 months or more of the year outside of the US. the majority of the time I have my iPhone (for the last year) and before that a cheap Samsung in airplane mode and have never been charged. If I was not in airplane mode and received a call I was charged whether I answered it or not. I was not even charged if I came out of airplane mode and it showed that I had a voice mail as long as I didn't call to check it.
The issue in getting charged is not in receiving an email but in receiving the call. If you are in airplane mode you will be fine.
I would suggest that you take the SIM card out of the phone long before you even arrive. Put it somewhere safe so that you can pop it back in once you reach your home country.