I have same problem as **mahdavi**. I bought my phone in Israel.
During a call every thing is ok until I click the speaker.
I can hear the peer clearly but he/she can not hear me clearly and I should shout.
I was advised by the retailer to raise volume of the speaker, during call, to maximum. He told me that it influence microphone sensitivity too. I did it, It did not help.
I have the feeling this is a general problem in Nokia 930.