Okay, I'm sure this is not the volume problem some of you are having, but it was for me and another person in the iPhone workshop I went to. Both of us were barely able to hear anything when we were talking on the phone. Then it occurred to me that maybe the plastic cover that came over the screen (which both of us had left on) was covering the speaker. I checked it out and sure enough that piece of plastic was over the speaker. I removed it and now find the volume level to be fine when talking on the phone. Like I said, this probably isn't the issue for most of you, but it might be for a few of you.