Change status scheme for document type

Hello!

I have created some document types for service tickets.

Afterwards I created a statusscheme for the document types. Now, I noticed that I'm not able to change the status scheme of the created document types.

I also tried to delete this document types but the button is disabled.

I read following in the setup guide from C4C: IT Setup Guide

Deleting a Document Type

1. 1.Select the entry you want to delete and click Delete.
2. 2.Save your changes.

Note

You can't delete document types that are used in your tickets.

However I'm not able to delete my used ticket so I tried to set them as irelavant. But still I'm not able to delete or change the document types.

In which way can we change or delete the document types?

Thnx in advance!

Regards

Arian