Hello Mithun,
Is it the free 1000 international long distance minutes you are referring to?
If so it is only to these select countries:
Australia
Bangladesh
China (including Macau)
Germany
Hong Kong
India
Italy
Mexico
Taiwan
United Kingdom
If you made calls to the US and was unaware unfortunately there is nothing that can be done because you made the calls so the charges would be valid.
If you will be calling the US often you might want to consider the unlimited US add-on, you can get more info here.
