To my knowledge, I have always been able to use Safari while I was talking to someone on the phone. I have noticed that since upgrading to iOS 4.0 (still using 3GS) the "3G" doesn't show up while I'm on a call and I can't use Safari. "Cellular data connections are not available during this call," is what appears. Sometimes I can initially connect to Safari but the connection is soon lost and that error message appears. Any thoughts? Thanks!