Really works done it on my phone
Download setool2 from here
and next download SIMLockPatchGen.exe from here
Then find out what firmware is on your Phone by entering >*<<*<* (< is left on the direction botton and * is the button below 7)
You will need to download the firmware from the internet and then use the simlockpatchgen on it to create the patch!
Next you will open setool2 and select you phone (eg. w300i) then enter the firmware file in to the firmware upgrade pack area and enter the new patch in to the misc file area and then select write script and make sure wen connecting your phone that it is of and is charged follw the instructions indicated in the window near the bottom left!
Try follow my poor attempt of instructions it worked perfect for me so it should for you!!!:D:D:D:p