I got an iphone from an apple store. does it mean that I can use it in another country (since it must be unlocked)?

That depends on whether you purchased an unlocked phone or not. You don't give us enough information on which to base an answer.

What does your receipt say?

With restriction and proper procedure, you can probably use the iPhone in another country. As KiltedTim mentioned, you've failed to provide us with sufficient information. Since you bought the iPhone form an Apple store, why didn't you speak with someone at the store?