I live in an area where 2G is stronger than 3G (I seem to get 1 more bar when I turn off 3G). However, once I do that I get a weird buzz sound (like there was a static interference). Its the same kind of sound you here from computer speakers when you place a phone near them. But I tested it away from potential interference sources. Once I turned on 3G, the voice was clean and there was no more buzz sound!   I hear those sounds on low when I put the phone to my head. When I  use the speakerphone I hear no static sounds.   I had Blackberry Curve 8310 before with ATT that did calls on 2G only and never had this issue.    I am using phone without case waiting for a free one in the mail, but I don’t hold the bottom and it still does that.    Should I take it to Apple Store and diagnose it? Did you have the same problem?