Audio of other apps and notifications very loud during calls

Hello, I’ve bought iPhone 14 Pro Max not long ago and ever since then, whenever I am in the call or on Discord, every other sound is very loud. iPhone used to reduce the volume of other apps while on a phone call, which I was told was a feature, but now it is exactly the other way around and during any type of phone call, whether a normal one, or Messenger or just hanging with friends on Discord, all of my iPhone sounds (other apps, music, notifications , locking sound…) are at full volume with no way to adjust them. It is very annoying. iOS 16.3.1 (updated), tried reinstalling all the affected apps, tried every sound setting, nothing worked so far.

Any and every idea for a fix would be appreciated. Thanks!