How do I turn off sound in Messenger?

I have gone here: Facebook App > Menu > all the way to the bottom part > Settings and Privacy > Settings > Media and Contacts > Sounds > In-app sound > I have turned it off.

But stupid Messenger still has sound.

Why is this happening? Have I gone to the wrong setting? I am using an Apple iPhone 5s but what's of concern is that the App is version 234.0

What the ****?

No wonder that I am having problems.