For disabling Ticket surveys :
By default, survey emails are enabled only for 'Closed' ticket status. You can disable the survey emails from Admin CP > Tickets > Statuses > Closed > Options > Send satisfaction survey email = No . With this, whenever a ticket is changed to this ticket status, a survey email will not be dispatched to the user asking for rating and comments.
For disabling Chat surveys :
To disable the chat surveys, just empty the contents of the following phrases from Admin CP > Languages > Phrases :