@Joycie: Are you using the phone's internal mic while on a call? If you switch to loudspeaker, or use a headset, does the issues persist? Further to the advice offered by @nowdeleted, head to the Samsung Members app > Get Help > Diagnostics > Start > Mic, and run through the on screen instructions. Similarly, open the Phone app and type in *#0283#, then select “Start: RCV_1stMic” and speak into your phone like you’re on a call. Does the issue occur in the playback? Once you’ve done that select “Start: SPK_2ndMic”, talk into your phone like you’re talking to someone on speaker phone. Let me know how you get on.
