Q: i do not wanna use credit card

I don't think that the feature to remove a credit card is available in all countries. Have you been using this credit card? If you have and you can't remove it and if you just want to download free apps or use an iTunes card, then it should not affect your credit card anyway.

I have a credit card on file with iTunes and haven't had to use it in over two years because I keep adding iTunes gift cards to my account.

If you just created this Apple ID and realized that you didn't want to use a credit card, then you created the ID incorrectly. There is a very specific way that you have to create an Apple ID if you do not want to enter any credit card details at all.

Creating an iTunes Store account without credit card - Support - Apple

How to Get Apps From the App Store Without a Credit Card

http://ipadhelp.com/ipad-help/how-to-get-free-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

http://support.apple.com/kb/ht2534

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.

 Cheers, Tom