The person on the other end of the line cannot hear me clearly.

If the problem is not coming from your (or your correspondent's) network reception quality, you can try following this procedure to change the phone settings for the Echo Canceller/Noise Canceller (EC/NC) mode, which reduces echo and noise in phone call conversations:

IMPORTANT: The following procedure may differ depending on the product. If model-specific information is required to complete any of the steps in this solution, refer to the operating instructions supplied with the product.

1. Press and hold the MIC button during a call.
2. Set the mode to EC/NC-1 or EC/NC-2 to adjust.

NOTE: Surrounding noise will interfere with the microphone. Try to reduce the surrounding noise as much as possible. Roll up windows, turn down the air conditioner, etc.