You can't have "none" as an option if you have any subscriptions on your phone. See: If you can't choose None when you edit your Apple ID payment information - Apple Support
You can't have "none" as an option if you have any subscriptions on your phone. See: If you can't choose None when you edit your Apple ID payment information - Apple Support
I don’t have any subscriptions or unpaid apps that I can see
Read the whole link.
how yo download a free app without a credit card?