Unable to make purchases using my Apple Account

Ironically, Apple doesn’t actually provide a way to contact “iTunes Store Support” on its support pages ➔ Contact - Official Apple Support or https://getsupport.apple.com/

On the Contact page:

Select “More products”

Select “iTunes Store”

Select “Other iTunes Store Topics”

Scroll down to “Or, tell us in your own words”, and enter “Your purchase could not be completed”.

This takes you to "Your credit card was declined"

See if adding a working credit or debit card is what it wants. If you have already entered one, check and make sure there is no error message in red next to it. If there isn’t, scroll down and tap “Contact”. Alternatively given Apple a telephone call. This support article has various country telephone numbers for contacting Apple for support and service ➔ Contact Apple for support and service - Apple Support For some countries look under “Other” listing at the end of each region. Not every country has telephone support.