I am currently using an Airtel sim card and will be going to the USA at the beginning of May. I would like to know whether I can use my airtel sim card in the USA, and exactly what kind of charges I would incur when making or receiving a call. I would also like to know about data usage. Some time back I did hear about Airtel launching international sim cards, what exactly is this and how does it work. What works out to be better using the sim card on roaming or the international sim card?