Payment

Here are a couple links that will get you started –

Subscriptions and Billing - Apple Support:

https://support.apple.com/billing

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

https://support.apple.com/en-us/HT203005

Sometimes, from the time of purchase using you credit card to the time the charger is posted too your Credit Card can take some time.

That, or did your Credit Card Company specifically alert you directly that a charge from Apple was rejected ??