how to change my number?

Try this, it's the one for your version.

VERITAS Pre-1999 panel

enter Existing Code *,*,*,*,
enter 0,0
enter 0,1
enter New Code *,*,*,*,
press PROG
press RESET

acorn
April 2011

Not sure about this, they changed about 2000. I assume that you do not have manual, Get it here.
http://www.thesecurityinstaller.co.uk/community/index.php?app=forums&module=forums§ion=attach&tid=961
But to change code.

Enter Existing Code
Press Prog
Press 60
Enter New Code
Press Prog
Press Reset

SD
April 2011