My iphone sound is garbled. Everyone sounds as if they are in an echo chamber. Suggestions?

If you hear distorted sound from your iPhone, read this support article --> If you hear no sound or distorted sound from your iPhone, iPad, or iPod touch speaker - Apple Support

Does it sound like this regardless of who is calling?

How about when doing something like playing music?

Hello ~ Do you have a case or screen protector on the iPhone? Remove them and try. If not try a forced restart by clicking on below

Force restart iPhone - Apple Support

~Katana-San~