Try using the *7465625*228# unlocking code first. If this codes doesn't work, then lets go to flashing procedure.
All you need is usb cable for Samsung, installed and well configured usb driver that can be found in the previous post and the V804ss Unlocker package by Spunlock.
1.First make sure the fone is fully charged before you go to unlocking procedure.
2.Turn OFF the phone, then hold the “9” button in the phone while pressing the “POWER” button. The phone should display an empty Light Blue screen which is called the Bootloader. Then connect the usb cable to fone.
3.Open the V804ss_MDL...exe
4.Put the BOOT_loader.bin to BOOT Loader window.
5.Put the VMSZT.bin to Modem code window.
6.Put the RSRC_v804ss_vodafoneKK.cnt to RSRC window.
7.Put the RSRC2.cnt to RSRC2 window.
8. Put the FactoryFs_v804ss_vodafoneKK.bin to Factory FS window.
9.Now Click the Apply Configuration button. The sw will automatically search what com port no. the fone was assigned.
10.After the sw detects the fone, press again the Apply Configuration or the GO1 button. Wait for approx 5mins until flashing is done.
11. Then the fone will automatically format, then after a few mins the fone will ask you to restart the fone.
12. Now, put a non-vodafone sim then power the fone until it search for network. Done.
Note: Some fone will not automatically accepts a non-vodafone sim after the flashing procedure. But don't worry. All you have to do is put a vodafone sim and power on fone. Now enter the unlocking code *7465625*228#. Then Power off fone, put a non-vodafone sim, power on fone and its done.

This sw is better because it doesn't affect the fone's IMEI and the Japanese language was retained. Coz the sw uses an original v804ss flash file.

See More: samsung 804ss unlocking