I would think that when they received the charge is irrelevant, it's when you used the data that matters. What if, on particular day (say March 15, 2010) in China (or any foreign country), you used a HUGE amount of data and it took the local provider a month to get the "charge" to Verizon (say on April 15), would you be liable for international roaming on April 15th when you were happily ensconced back in the US on Verizon's network?

With a copy of your boarding pass, itinerary, hotel check out, U.S. Passport arrival stamp and country departure stamp you could show you weren't "there" to be using data. Plus, your provider's system (which they control and shouldn't have such a lag or trickling in charges), would also show you turning on your phone upon arrival back in the states and starting to use their data system. That said, this wouldn't be an argument that I'd expect you to win with a front line CSR person but you seem to have won.

I actually keep the service on for a couple or three days extra for a different reason. If I'm delayed abroad for a day or two, I don't want the international roaming plan to turn "off" while I'm still/stuck abroad and start running up international roaming charges.

As an aside, based on an earlier comment, it seems the MiFi works abroad. Really? What countries? Does the '$2 per day for unlimited data' while abroad plan apply to the MiFi? I'd appreciate any links as I've got to take another look at the MiFi as a replacement to my T-Mo USB laptop stick (slow, one computer at a time - unless you get a router - and EXPENSIVE to use abroad).