Create or use your Apple ID without a payment method: https://support.apple.com/en-ca/HT204034
Change or remove your Apple ID payment information: https://support.apple.com/en-ca/HT201266
Why can’t I select None when I edit my Apple ID payment information? - Apple Support: https://support.apple.com/en-gb/HT203905
Pay an unpaid balance in the iTunes Store - Apple Support: https://support.apple.com/en-us/HT203005
Payment methods you can use in the iTunes Store, App Store, and iBooks Store - Apple Support: https://support.apple.com/en-gb/HT202631
Contact - Official Apple Support: https://support.apple.com/contact