Regarding cancellation of purchase

You cannot. Pending payments must be completed correctly, they cannot be cancelled. Once completed a refund can be requested.

The only way for a card to be valid is for it be chargeable. So completing the payment correctly will in itself do this.

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

Make sure you have a valid payment method on file that can be charged for the pending payment.

See the link provided above. You need to add a valid payment method to the Apple ID.

See also here: Change, add, or remove Apple ID payment methods - Apple Support