Separate Sound not working on call

[Ace16]

I own the Galaxy S24 Ultra  and the Separate sound feature doesn't work when I am on call. 

So for example, I want to go on a call and have that go through my phone, but listen to music, and have that go through my speaker. 

But when I go on call, it can only play music through my phone if I have it going through that, or if my call is going through the speaker, the music does, but my speaker doesn't have a mic on it.