sounds like a hardware failure. You should bring your phone into Apple for exchange.
It's not that they're bad. The iPhone warranty is generally valid only in the country of purchase. To have your phone serviced by Apple, you'll need to send your phone to a friend or relative in the US and have him or her bring the phone into Apple. Once fixed or exchanged, that person would send the phone back to you.
Alternatively, you can search Google for a 3rd party iPhone repair shop near you. Of course, you'll have to pay for repairs and your warranty will be void, but it might be the only practical thing for you to do.