Wrong. Please try it before you post this mis-information. The Thunderbolt is the ONLY phone on Verizon capable of doing 3G/talking at the same time.
If you turn off your WiFi and set your phone to CDMA Only (Not 'CDMA/LTE') which will force it to only be on 3G, you will NOT be able to browse the internet while talking on the phone. I just tried before I decided to write this as I don't like being wrong. Its been stated several times that WiFi and 4G are the only methods of getting data while on the phone, and its the truth.
Brian