I don't want to sound like a smartass, but it seems you didn't look into this purchase very much. The news of the iPhone 5 release has been posted everywhere for months. Do you live in the country where you bought it? Doesn't the store allow returns? I'd certainly ask them.
Ebay it and you'll get a really good price because if you bought it in Malaysia it must be factory unlocked which makes it more valuable. Make sure you say that in your ad. I bought mine in Germany really cheap and factory unlocked. Best purchase I've done in a long time.