Phone function not working.

[Speed_419]

The phone function of my phone won't work. I can use it like a PDA, but I can't get the phone portion of the phone to work at all. Won't do anything. I do have a spare parts phone that I could use, but what I was wondering is this. If I swap the radios in the phone, will it fix the issue with the phone not engaging, and second will it still have the same ESN, or will it get the new radio ESN?? Any help would be appreciated.