Q: using iphone 5s caller cannot hear me unless I use speakerphone

Did you already try to force reset the phone by holding the sleep and home button for about 10sec, until the Apple logo comes back again? You will not lose data, but it can cure some glitches.

If this does not work, and to make sure the issue is not software related, setting it bak to factory settings would be the next step after that.

Use iTunes to restore your iOS device to factory settings - Apple Support

Also check this article:

Get help with the microphones on your iPhone, iPad, and iPod touch - Apple Support