UNLOCKING for verizon network

I was wondering if there is any way to unlock a AT&T phone to work with verizon. I have at the moment a LG chocolate and i believe its CDMA and i need a second phone for business and i got a Samsung SGH-D807. Is is possible to get a GSM phone unlocked to work on a CDMA network such as verizon??

ok that makes sense. thank you!