See this if you cannot select None. If you can't choose None when you edit your Apple ID payment information - Apple Support
If you do not have a credit card, then you would need to purchase an iTunes Gift Card and redeem it in your Apple account so you would have a credit balance. iTunes requires a credit card to validate who you are and if you are authorized for the iTunes Store you are trying to use. See this information. Create or use your Apple ID without a payment method - Apple Support However, if this Apple ID has already been created, the only choice is to add a card, validate the account, and then you can remove it.