A:AnswerSure, it will work anywhere there is a cell tower nearby. It's like using the internet in your phone, only this is a hotspot and you can connect other devices.
A:AnswerYou can buy a Simple Mobile Data plan online or on a card at stores like Best Buy and I am sure elsewhere. The cards are just a way of paying for a plan - they have no SIM card - which is already in the device. You can top up on the the Simple Mobile app - if you burn through your data quickly.
A:AnswerIt will not work in dead areas. I purchased it to have when I’m out but found in an area that when my phone have a problem connecting with wi fi, so does this device.
A:AnswerIt doesn't matter that you have ATT, the Moxee Hotspot from Simple Mobile runs on the Verizon Network, so if the place in Japan you are visiting runs on the Verizon Network, you should be able to use the "WIFI" on your phone to connect to this device to have Internet browsing on your iPhone. You would want to check the Simple Mobile Website for the International coverage just in case.
A:AnswerI think it will work for you. You buy blocks of data and use it when you want and add new blocks when needed. I think its about $50 for 40GB. Check out expiration of the data, I dont know if they expire unused data after some time.