iPhone 4 My voice not hear by others when making calls

Hi,

I am facing with my iPhone 4, when I make calls to others, I can hear them but they can not hear me. I tried some options after seeing in internet by keeping the card board, but its not working.

Skype,voice memo and other apps are working fine, only when calling others not hear my voice.

When I check with technicians some of them saying its ic problem some of them are saying mic problem.

If any one had this problem and got any solution please respond to my mail mrsrini671@yahoo.com or reply to this post.

Thanks in advance.

Regards
Srini