just want to clarify my first post. you will not be charged for the free App. My understanding is that Apple uses your credit/bank card to verify your billing address. An application that they sell may not be licensed to be used in the country that you reside in, therefor, they need to verify that you live in the specific App Store country that you are signed in to.
How to Get Apps From the App Store Without a Credit Card
Creating an iTunes Store, App Store, iBookstore, and Mac App Store account without a credit card
If None is not available - On your computer launch iTunes and click "iTunes Store" in the left navigation pane. Click the "down arrow" next to your name at the top right side of the page and click "Account." Enter your username and password and click "View Account" to log into your account information. Next to your Payment Type, click "Edit." Select the "None" button and click "Done." Confirm that your card has been removed by returning to the Apple account information screen. Under Payment Type, it should say that there is no credit card on file.
PS You can't use a debit card.
WHen i registered for the first time it asked me for my credit card details and charged me some amount, now few days back i was trying to download a free app, it again asked me for my Cc details, assuming its a free app i verified the details but they charged me again. I fail to understand why i was charged for free app on app store??
can some one help me with this.