Customer raised a request with a wrong Customer Request Type(he chose "issue" while it should be a "request"), and we would like to change it for him instead of creating a new call again.
Since they are different issue types("Issue" is incident and "request" is task in our JIRA SD) , we found out that we have to move to the right issue type first. It successfully shows the value for us to choose. But then I still can't save the change for the field of Customer Request Type, as the screenshot below.

Can somebody tell me what I have done wrong or what else I should change?