"Spath, I was under the impression that airplane mode prevented your phone from picking up any unwanted roaming charges"
Nailit, yes it will do this to be honest. It would do that because it blocks signals going to the phone and from the phone, so if it's on airplane mode, the phone won't know where it is, so there won't be any random charges from anywhere.
However, you won't get these in Amsterdam I can assure you on that.
Times have changed though, and roaming charges are almost a thing of the past.. they certainly are in west Europe.