One of the speakers of my iPhone doesn’t work

Which speaker do you think doesn't work? There are two speakers on iPhone. One at the top of the screen you listen through when your ear is up against the phone on a call. And ONE on the bottom of the iPhone, to the right of the lightning port. The one you may think is a speaker to the left of the port is actually the microphone.

Here's a diagram for an iPhone 12 Pro Max; similar diagrams for other phones can be found on Apple's web site.