Headed up north to canada for a few days, and would like to avoid any surprises when it comes to my bill. I keep "enable data roaming" off as a matter of course, so that's already done. It looks like if I also disable "enable cellular data" that I should be ok (right?) but to be paranoid is there a way to essentially turn the device into a wifi only device (ie "airplane mode" + wifi)? It looks like my best bet would be to disable 3G, data roaming & cellular data - if I do those three will there be any way that I could get extra charges while I'm there?