1) Go to eZee Frontdesk Configuration>> Configuration >> User >> Select and Edit User from the list

Please refer below screenshot  

2)Once you edit User Goto Operational Privilege >> Find with Keyword “ability” click on find icon

so it will show privilege “ability to change tarrif after check in” that is what you can uncheck >> Click on save.

3) Restart eZee Frontdesk >> Login with that user >> Open Room and Check with rate Information Tab >>So  You will come to know that after check in “Apply Changes” is degrade

Please refer below screenshot