How to clear up an unpaid purchase

if it was me then I would read

If you need to change or update your Apple ID payment method - Apple Support

and

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

and if I still had issues then I would reach out to their support  Apple Support

And or  Contact - Official Apple Support

You need to add a valid new payment method.

Based on your country of residence and country you have selected under your Apple ID --> Payment methods that you can use with your Apple ID - Apple ...

Have you a Debit/Credit card that is issued to you that is valid internationally and is from the same Country / Region as your Apple ID.

Know it here --> If your payment method is declined in the App Store or iTunes ...

Check the following

1. The payment method that you are adding is of the same country as that of App Store Country on your iPhone
2. You have a valid payment plan debit/credit card from an authorised bank from the same country
3. Payment methods that you can use with your Apple ID - Apple Support
4. Learn more about family purchases and payments.
5. Please check if your Debit/Credit card is valid internationally