How do I stop getting charged for an app I deleted?
There is such a thing as app subscriptions which will just be billed to the card associated with the app store.

Go to the app store, scroll to the bottom click your username, click view account, then hit Manage, then find the app that has a subscription added to it, click it and then hit the automatic renewal toggle to off.

You had purchased the app subscription which is why it's billing you