Make sure to use a sim card that is not accepted by that phone!

enter e2p reset code
*2767*3855# let it reboot

then enter...
*7465625*638*00000000*00000000# (to change NCK code to 00000000)

then enter...
#7465625*638*00000000# (to permanently unlock the phone)

btw. make sure you back up everything you want to keep. the e2p reset code will wipe your phone memory clean.

See More: samsung t809 unlocking