Security code for Nokia 7373??

I have the Nokia 7373. I want to set the security code on my messages. I looked in the book that came with the phone which says it is a 5-10 digit code, it says you should try 12345 which I have. I haven't changed it all. Does anyone have any ideas what I can do??
I have tried all the following:
12345
1234512345
1111111111
0000000000
5555
5555555555

PLEASE HELP!!
I have tried 0000.
It isn't locked as it would have told me it was. It still lets me try to enter a security code.

This is strange, it should let you lock it. Maybe you can't just lock your mesg. maybe you have to lock the whole phone? I would try going to www.nokia.com and looking up he model # there. Or calling your service provider and maybe their cust. care can walk you through it!

dont carry on trying as the phone can be blocked if you carry on doing this
it is on your sim card box or if you dont have it go to your service provider

I am making a guess. Try a 4 digit number:

0000