Add new payment method is declined.

See the Apple Support article(s) below. Link to contact Apple Support in the article below.

Apple ID payment information - If your payment method is declined, or you have a billing issue with a previous purchase in the iTunes Store.    

Possible fixes.   Fix ‘Your Payment Method Was Declined’ Error In App Store

                              Payment method declined in iTunes or the App Store ...

If you have an active subscription, you can't remove the current payment method unless you can add another payment method that isn't declined.

I suggest you contact iTunes Support for assistance. See the Apple Support articles below for contact information.   

iTunes Support – world wide 

Apple Support schedule phone call      

If necessary, try Twitter

https://twitter.com/AppleSupport.          People have posted it may take an hour or more to get a response.

We are users like you, not Apple employees, so we don't have access to your data information, so we can't help.

Contact iTunes Support using the links above.