Try all the above (clean the small hole and the card trick), and if none of those work, resort to this: http://www.beijingiphonerepair.com/fix/d...-repair-iphone-4-people-cant-hear-me-i-cant-hear-other-people/ worked for me. Requires a pretty good open heart surgery of your phone, if your comfortable with that. Use the dissecting guide found on this website to get to that chip. Once you get to it, you have to carefully pry off the EMI shield, one little by little, one side at time and go around a few times. The tell all symptom for me was when using a hands free headphones, (the mic is in the button part of the headphones and not phone itself) and it still cut out during a call. Sometimes i hear static as well.