Xiaomi Mi Note 10s

@dikshabharti use a headset with a mic and see if the person can hear you with that. If so, it is most likely an issue with your mic. Of course, try a reset first and check all of your software settings. Check on something like this video for a few more software related tips.

IF you find that the issue persist, it might be time to replace the mic.Luckily the mic is mounted to the charging board and this easily replaced. Since iFixit does not have a guide for this repair, use something like this guide or the teardwon shown here https://www.ifixit.com/Teardown/Xiaomi+M... for the task. The first guide is for the Pro but it opens the same way. For the part, you are looking for a part like this It is readily available and many online stores. Make sure that you purchase one that is an exact match for your phones version.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.