The Casing & Protective Layer for iPhone 4 is Free, or Is It?
The free case program is no longer automatic, and it was never done in-store. You had to download an app to request your free case. (That was their way to make sure only one case was requested per-phone.) I'm also not sure if it was ever valid outside the United States.

To get the free case now, you have to call Apple support and complain about phone signal issues. You also have to ask them directly for a free case.

I have no idea if the same deal applies in Malaysia, but this isn't a case of the store trying to cheat you. They never gave away cases in-store.