I have a Nokia cell phone and I’m using the AT&T network here in the Bay Area in California.  I’m in an area where the 3g signal is mediocre at best.  However, whenever I am talking to someone on the phone, I tend to notice that parts of words I hear from the person I am talking to tends to cut out. 

For example, something like, “Hello, ho* are yo* today?”  I am not saying that this happens on Nokia phones only, I’ve noticed it on other phones as well.  I think it has to do with the switching between 3G and EDGE/GSM during a call.  So what I did was completely turn 3G off and to use GSM only.  I’ve consistently noticed less parts of words being cut off and my call quality more consistent.  Not all phones will allow you to do this.  But if you’re able to, give it a shot and let me know.