Calling sound not work

From what you are saying I can gather that your dock connector microphone is bad and you will probably need to replace the dock connector assembly as that is the microphone used during calls without speakerphone on and in the voice record application.

Can you hear other people during calls without speaker phone on? If not then the earpiece speaker is faulty as well.

Guide to replacing dock connector (which contains bottom microphone):

iPhone 4 Earpiece Speaker Replacement

Guide to replacing earpiece speaker (top speaker):

iPhone 4 Earpiece Speaker Replacement

You can get the dock connector from here:

[リンクされた製品が存在しない、もしくは無効: IF182-009]

You can get the earpiece speaker part from here:

[リンクされた製品が存在しない、もしくは無効: IF182-010]