To stop a podcast that's playing, you should be able to control the playback with an app notification. Which podcast app are you using? Does it have a notification that includes playback controls?
I don't use WhatsApp, so I can't answer that question directly. But again, if you're on a call and the WhatsApp app isn't open in the foreground, then there should be a notification in the status bar that allows you to either control the call directly, or quickly open WhatsApp up again to end the call.
01-24-2019 12:02 AM