Apple - Changes to OSi billing and compatiblity

On June 30, 2018, Apple will implement changes to continue to ensure your financial data is protected when you make purchases on the iTunes Store or App Store. 

Our records show that you may be accessing the store from an older version of iOS, macOS, or Apple TV software: 

iOS 4.3.5 or earlier 
macOS 10.8.5 or earlier 
Apple TV Software 4.4.4 or earlier 

To be able to change your payment information with devices running the software listed above, you'll need to update to a more recent software version. 

Learn more. 

Regards 

iTunes Support Team 
http://www.apple.com/support/itunes/ww/