Before deleting an employee, make sure that all attachments are disconnected from them, namely:
From groups.
From the incoming or outgoing direction of the number.
From IVR (interactive voice response).
From widgets.
Disconnect from all attachments, and then you will be able to delete the employee.
How do I delete one employee?
Click Employees
Click button "..."
Click Delete
In the modal window that appears, confirm the action with the Delete button.