I thought I have been able to in the past. I have an Epic phone. I am getting two different answers from Sprint . The store employees are telling me you cannot. I spoke to the advance techs over the phone and they said you can. I thought youcoukd and that was the whole point of the 3G network. I know you cannot while you are on edge but as long as you are on 3G I thought you would be able to (without Wifi).
Using data while on a call has never been a feature for Sprint. The 3G network for Sprint is not designed to do this since because it's a limitation of CDMA technology. This would be that case with Veizon and US Cellular as well since they too are CDMA technology. With that being said, voice and data CAN be used simultaneously but only on the 4G network, and/or wifi. This is because when you're using 4G or wifi, you are NOT taking up any channels on Sprint towers so CDMA can handle the voice request because the data is being requested from a non 3G Sprint network.
So again, 3G voice and data CANNOT be used simultaneously on the Sprint CDMA network. Voice while connected to 4G or wifi CAN be used simultaneously.
Hope this helps.
Sprint Advanced Technical Support