Ericsson T29s

Hi Peeps

Not sure if this is the right place for this query or indeed if anyone can
help anyway.

I have an old Ericsson T29s, I have not used this phone for a couple of
years but it is still in working order, I recently put a new sim card into
the phone, however I am unable to get past the following screen:

Phone Locked
-----------------------------
Phone lock code:

I cannot get past this screen (all recent codes tried, including that of the
sim card), will I need to take the phone somewhere to be unlocked or is
there anything I can do myself.

cheers