Hi there! I understand you're having trouble stopping the audio playback on the Chirp Audiobooks app using your iPhone 15. Let’s see if we can get this sorted out for you.

To start, could you let me know if you are able to pause or stop the audio at all, or does the app seem completely unresponsive? Also, are you trying to stop audio using the on-screen controls within the app, from the iPhone Control Center, or using hardware buttons like the volume or side button?

In the meantime, here are some initial troubleshooting steps you can try specifically for iOS devices like your iPhone 15:

1. Force Quit the Chirp App:
- Swipe up from the bottom and pause slightly in the middle of the screen to open the app switcher.
- Find the Chirp app’s card and swipe it up off the screen to close it.
- Reopen Chirp and see if the stop/pause controls work now.

2. Restart Your iPhone:
- Press and hold the side button and one of the volume buttons until you see the power-off slider.
- Drag the slider to turn off, then press and hold the side button to turn it back on.
- Open Chirp again and try to stop the audio playback.

3. Check for App Updates:
- Go to the App Store.
- Tap your profile icon at the top right.
- Scroll to see if Chirp has an update available. If yes, update the app.

4. Check for iOS Updates:
- Go to Settings > General > Software Update.
- If there is a pending update for iOS, installing it may fix compatibility issues.

If these basic steps don't fix the problem, sometimes apps can behave oddly due to corrupted settings or files. In that case, you might try deleting the Chirp app and reinstalling it. Just be sure your audiobooks are backed up or remembered in your account since deleting the app will remove downloaded files.

Could you try these options and let me know what happens? Also, if you notice any error messages or specific behaviors, that info will help me guide you better.

Are you satisfied with these suggestions so far?