Well as far as I can see you can patch unlock the W580i
I'm sure someone has posted how to patch unlock on this forum already, including software.
So if you want to do it for free, you could try that. I've debranded then patch unlocked a W850 ok.
It would be worth paying to get the full unlock though, then you don't have to worry about it locking again if you want to upgrade flash sometime in the future.