You did it incorrectly. You can't create an Apple ID without a credit card unless you do it in a very specific fashion. You either have to enter a credit card now - and then hope that you get the None option when you try to edit payment information - or you have to start all over again and set it correctly.
This explains how to do it.
You need to sign out of the ID that you are currently in - Settings>iTunes & App Stores>Apple ID and you will need another email address now because you cannot use the email address that you used for the first Apple ID.
You can create an iTune and App Store account without credit card details
1. Sign out of current Apple ID if you are sign-in to one (important)
2. Go to App Store and select a free app
3. Tap INSTALL APP
4. Create New Apple ID
5. Confirm Your Country
6. Agree with Terms and Conditions
7. Fill in your Apple ID and Password (you must create a new Apple ID; don't use your old Apple ID)
8. Create and answer your secret question
9. Select NONE for Payment Method
10. Fill in Billing Address
11. Submit application for new Apple ID
12. Wait for verification email
13. When email arrive, verify your account
14. Start downloading your free apps