I was in Hawaii for a week, and my account was set to the default cap of $150, so that as soon as I reached $150 in roaming charges, data roaming would be automatically switched off.
I arrived in Hawaii on a Friday, then in the rental car used a bit of Google Maps, then over the course of the next few days a bit of Facebook, WhatsApp, stuff like that. Dropbox and Google Play were set to upload/download things over wi-fi only. Basically I used it sparingly, no YouTube, taking pics and emailing them, etc.
My data roaming was stopped on the Thursday, which I thought was pretty good considering how much driving we'd done and so on. I only had two days left there and had no more need for Google Maps or anything, but still wanted to use WhatsApp, so I overrode the limit so I could continue to roam.
Three days later when I'm back in NZ my roaming bill has shot up to $460 versus the $150 it was when it was disabled.
Do carriers overseas take a while to send the charges back home? Because that's the only reason I can think of as to why it went up by so much. I hardly used the phone at all after I had roaming turned back on, so I just wonder if during those first days only some usage was being billed then at some point it all caught up and evened out.