Apple did not let anything go through. If you initiate a charge, Apple attempts to charge it. If it cannot be charged correctly it stays pending. The fact it is pending, means it "did not actually go through".
Also, Apple is not in the business of managing your finances, the automated system does not know whether you have the money for something or not. It just attempts to charge whatever you tried to buy, or any subscription that tries to renew.
You should know if you can't pay for something and not try to buy it, or let it renew.
You still owe that money now though, because you started the transaction.
If you did not want the app, the only one that can cancel its associated subscription is you. Nobody else has the right to cancel anything you start but you. People would be up in arms if Apple cancelled subscriptions unilaterally because they could not be charged. Apple has no way of knowing you want something cancelled unless you cancel it.
When you download an App you agree that apple will charge you until you cancel it. You agree to this and are bound by the legal agreement. If you want something cancelled, you need to do so yourself. Don't expect anyone else to do it for you.
Now you need to let it complete, then cancel whatever caused the charge and request a refund as has been mentioned many times in the very thread you replied to.
click here ➜ If you want to cancel a subscription from Apple - Apple Support
click here ➜ Request a refund for apps or content that you bought from Apple - Apple Support