Your t-610 is a triband phone. What this means, as Giaguara was saying, is that you can use it more or less anywhere in the world with a GSM network. Most countries' networks run on 900 or 1800 MHz and most phones can work with either. The US uses 1900 MHz but some newer mobiles (like the t68 and the t610) will work on this frequency too. Check out the roaming costs with t-mobile, it might not be worth buying a pay-as-you-go sim if you're only going to be in, say Mexico, for a week. On the other hand, I don't know about other countries but a pay-as-you-go sim in the UK will cost $25 - £40. Just depends on what you think will be better value for you, since you'll be in India for a month, that might be better. Also, check to see if you can make data calls on pay-as-you-go. Hope that helps.