I cannot download anything from the app store due to debt

Click here-> https://finance-app.itunes.apple.com/purchases

Find and cancel any subscriptions by following the steps here: link-> How to cancel a subscription from Apple - Apple Support

You will need to successfully complete the pending charge to re-verify your account and be able to use the App Store again.

Once completed you can request a refund: click here-> contact Apple Support

Yes. You need to pay off the pending charge to clear your account of dues, then you can request a refund for it.