I have installed application core template and help desk template. I am facing
problem with permissions of the help desk site.

Here is what I want:

i. User opens a case

ii. IT Manager assigns the job (automatic assigment according
to category or keyword would be wonderful)

iii. IT Worker does the job and close the case

I don't want users to update the case after it is being processed.

If I put the ordinary user to Visitor group, s/he can not open any case

If s/he is a member, he can open a case but he can also change the state and
even close the case(which i do not want).

Also I do not want users and IT workers to access the reports.

Does help desk template can achieve this or did i completely misunderstood the
concept of the template?