[PPCFreak]

Sounds like your phone is stuck in EV-DO Only Mode.

Check PST ( #778 ) and at the top left where is says display, change to Modem Settings. Look at HDR Hybrid Preferred. Make sure that is set to Enabled.

You will need to edit PST if HDR Hybrid Preferred is not set correctly.

Dial #778
Click Edit
Password: 000000 (if Verizon)
Change upper left pull-down to Modem Settings (it will say Display at first).
Change HDR to Enabled.
Phone will re-boot.

Then try your calling again.

I had this same issue before and the HDR setting was messed up under Modem Settings.