@marzdgzmn 

Hi,
You can check if the following steps help the reported case.
    1. Adjust the volume of the camera's microphone and speaker to the maximum, and test speaking through the phone or speaking in front of the camera to see if there is any sound.
    2. Make sure that there are no obstructions covering the microphone and speaker on the camera.
    3. Ensure the camera is positioned to allow clear and unobstructed sound reception.
    4. Check if your phone is in silent mode and increase the media volume.
    5. Factory reset the camera and reconfigure it for a try.
Best Regards