I live in Canada but travel to the States. Can I just drop into a 7-11 or similar store to buy a new SIMM card to use 3G? How am I charged for use? Are the usage charges reasonable? Do I give a credit card? Is a Canadian card okay? I guess i shouldnt try using my Canadian simm card or there may be huge charges? What about countries other than the States, does it work the same in other countries? How exactly does this all work?