I need to add a new payment method

My payment does not work. I have removed an old card on the apple pay and delivery. My iphone has not been safty copied in 6 weeks. I can not add my new card on the settings. I dont know why i can not do this and need help. Because my store space is full. I need to add my new debit card so i can add store space and safty copied my iphone.

[Re-Titled by Moderator]