Phone is only vibrating, no sound.

My IPhone 11 is only vibrating, no ringtone. I checked the settings and everything looks ok but when I push the button on the side to increase the volume, the volume is turned up. When I push the side button up though, there is a message that comes up at the top that says Ringer and there is a red bell with a slash through it. Can someone tell what I'm doing wrong. Thank you.