Please help - Motorola 120e reception

My girlfriend replaced her phone (alltel) with a motorola 120e model. She
seems to be not getting good reception. Someone will call her and on THEIR
end it rings, but not on hers, or it will go straight to voicemail.

Is the 120e and better or worse in regards to reception compared to other
models? I suppose not fully understanding how they function adds to the
confusion. I assume there is some kind of contact between a cell phone and
the towers all the time.

chaz