Volume of Ringer, Alarms, Texts, Decreases Immediately When I’m Near my iPhone

I’ve had this problem before that even some Apple employees didn’t know how you fix until AFTER I paid $75 to get a replacement phone which had the same issue. Whenever the iPhone Is making a sound and I reach for it, or am close to it, the volume decreases dramatically. It turns out that It’s in the settings but i can’t remember the name. Anyone?