how to reset the alarm system when you have no code number?

I have a similar problem. I guess the resetting procedure is available only to registered service companies to avoid disclosing information that can be used to disable some else's alarm. An option may be replacing the control unit (mine costs less that a call out), but I am not sure it will do the trick and I don't know how to replace the control unit either (Texecom Veritas 8 Compact). Any clarification/suggestion welcome.

ThisIsMe
January 2010