it depends upon which phone, i mean 3gs or 4.
if it is iphone 4 then forget about it except using turbo sim 
still the problem is the jailbreaking. there is no unthetred jailbreaking for this version.
 meaning everytime the phone restarts it stuck on apple logo and u have to activate using redsn0w which is painful.
 
if it is 3gs then use redsn0w 0.9.6RC16 and do use ipad baseband that way it will be unlocked.
But i am not sure that there is unthetred jailbreaking for this version too.