Q: Hi guys ,i should delete credit card form my apple device

If you want to remove your credit card from your iTunes account (it's linked to your account, not the device) then on an iOS device (iPad, iPhone or iPod Touch) tap on your id in Settings > iTunes & App Store (Settings > Store on iOS 5 and below) and tap on 'View Apple ID' on the popup and log into your account  - that should give you a payments link on your account's page. Or you can do it via your computer's iTunes by going into the Store > View Account menu option and logging into your account, and on your account's details page there should also be a payment link.

Changing payment info : http://support.apple.com/kb/HT1918

If you don't get the 'none' option showing on your account : http://support.apple.com/kb/TS5366