Originally Posted by kms108
you don't need the menu for the ussd, korean version has their own set of ussd, they are different from the international version, some are the same , but most are different.
Please forgive me as I'm a total noob, but after your last reply it hit me: we're probably talking about different USSDs. I meant that my operator USSD codes didn't work, the ones that I send to find out my remaining balance and to also enable/disable services etc. (e.g. I would send *444#2#1 to find out my remaining balance), not the phone's own USSD codes (like the service menus etc, e.g. the IMEI check with *#06#). Operator USSD codes just don't work - the phone either sits trying to connect for a few minutes (locking the phone down during this time), or just says that the signal is too weak. So I guess I do need to install a different firmware to fully unlock it.
Thanks for trying to help though, I'm learning new stuff!