Problem with speakerphone microphone during call

[antoninosignorello]

Hi, I have a refurbished iphone 11. My problem is this: when I'm on a call with another person and I've turned on the speakerphone/speakerphone, if I and the other person talk at the same time, the other person doesn't hear me. The problem does not exist if the loudspeaker is turned off. If we talk at the same time, the other person can still hear me, hear the voices overlap. Could you help me?

 

[Ledsteplin]

Open the camera app. Record a video while speaking at the top of your iPhone. Then switch to the other camera. Then record another video same as before. When you play them back, you should hear your voice clearly. If you do, then the issue is with the other person. If you don't, you might contact Apple Support for help.