There are normally some hoops you can jump through as you create your iTunes account that workaround the need for a card, otherwise once the account is set up iTunes may still expect you to provide one, which you can subsequently remove. If you don't have or want to use a credit card at this time you can try this method using iTunes on a computer...
- Enable the menu bar if needed with Ctrl+B (Applies to Windows only)
- Sign out of the iTunes Store from the Store/Account item on the menu bar
- Go to iTunes Store home page
- Go to Quick Links > Redeem
- Sign in with your Apple ID
- Go through the screens, accepting the EULA, etc. You should arrive at a Review Payment screen where one of the options is None - select this and continue. You shouldn't actually need to redeem a new voucher/card.
It is worth noting that one of the functions of the registration is to prove you have a valid billing address in the region whose store you are trying to use.
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