Follow the below path to unassign the miscellaneous fee to students

Method 1: With The System Admin Access

Finance --> Fee Management --> Unassign Misc Fee To Students (Bulk) --> Select Branch, Class, Misc Fee Types and click on Get --> Select the students --> Unassign

Method 2: With the Branch Level Access

Finance --> Fee Management --> Misc. Fee Assign/Unassign --> Select the Misc Fee Types, Class, Section, Student Status and Click on Get --> Manage Misc. Fee --> Select the students --> Unassign