Can i unlock an AT&T iPhone 6 to place my sim card from my Verizon iPhone 5s in it?

Can i unlock an AT&T iPhone 6 to place my sim card from my Verizon iPhone 5s in it?

Yes you could unlock an AT&T phone but no you can't use a Verizon SIM in it since those are only for LTE use not calls/texts since Verizon is a CDMA network not GSM like AT&T.