Can’t purchase

If the purchases are from the App Store or iTunes:

Wondering if Apple support's online articles can help:

What to do:

If your payment method is declined in the App Store or iTunes Store - Apple Support

or

How to: Add a payment method to your Apple ID - Apple Support

or

If you can’t download or update apps on your iPhone or iPad - Apple Support

or

How to: Manage your iTunes Store purchases and settings on iPad - Apple Support

If needed:

The websites below have "Get Support" links (eg: online chat, phone, eMail etc) at the bottom:

App Store Support website:

App Store - Official Apple Support

or

iTunes Support

iTunes - Official Apple Support

or

Apple have a billing page with links to various options online:

Subscriptions and Billing - Official Apple Support

All the best :-)