[Plugin: Contact Form 7] [contact-form 404 "Not Found"]

Hi all
I am finish a project after 2 developers stucked on this website:

Link to contact form

As you can see we get an error: [contact-form 404 "Not Found"].
We are using CF7 version 2.4.5
I thing it is a problem with mod_rewrite.
As I was told the administrator of the server does not allow mod_rewrite so they are using permalinks with index.php in the middle of url so that you do not get 403 error.
Permalinks: /index.php/%year%/%monthnum%/%postname%/
I have changed it to /%year%/%monthnum%/%postname%/ and I got error 403.
I tried to delete plugin and reninstall it and the same error happends.
Also I have made new contact form with different name and still the same problem.
I have also tried to insert the function into theme file and still the same error.

I have installed Simple Modal Cotact form and it works fine.

Someone have any idea what could be wrong with it?

Thank you.

http://wordpress.org/extend/plugins/contact-form-7/