Purchase storage

There are a couple of possible reasons why payment information cannot be updated. But if you are being advised to contact Apple Support, then you should probably do so. In my experience, Support, particularly when it comes to payment stuff (go figure! :-)) has been very capable and responsive.

Good luck!

JDee

As the message states, Contact iTunes Support for assistance. See the Apple Support articles below for contact information.   

iTunes Support – world wide 

Apple Support schedule phone call      

Starting an online chat with Apple Support 

If necessary, try Twitter

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