While looking into various things for Op Wombat I came across this info and advice on mobile roaming and how to try and avoid the bill from hell.
Now I know it's a UK site but I'm sure with most phone companies being global beasts similar pitfalls and the ways to avoid them would apply to you guys too so if nothing else it might help give a few ideas of what to look into as an alternative or questions to ask your own provider.
http://www.moneysavingexpert.com/phones ... ming-calls
Despite the slightly cluttered look of the site the guy is reputable as a financial expert here http://en.wikipedia.org/wiki/Martin_Lew ... rnalist%29
Regards
JAS