not sure... It`s may be not the PIN for the SIM card but the PIN for the phone lock function! If you entered the phone lock PIN earlier I hope you will remember it. If you bought your T830 as used device (e-Bay or elsewhere) contact the previous owner for the PIN. May he remembers.
Last you only have the change to send it to Fujitsu or a support partner for unlocking, ask for the unlock charge prior to do so .