[quick99si]

What you want is to enable DDTM aka "Data Dedicated Transmission Mode." To do that, you're going to need to enable that option in your phone settings, and then turn it ON + soft reset.

Or if you have your MSL, enter ##000000# in the phonepad where the 0's represent your MSL, then look for DDTM in the EVDO menu.

I guess another way would be to force your device to "1x" mode. With an active data connection in 1x, all calls are go to voicemail automatically (the way DDTM would work under Ev).

Oh, and one last thing that may work would be a call filter like Magicall that immediately hangs up incoming phone calls. When done automatically, it may actually be quick enough to keep your data session alive.

Last resort, send a mass text to your entire phonebook and area code asking people not to call you for the next 1-2 hours. Don't forget telemarketers and people with upcoming unexpected emergencies.