The sub-header and the button labels can be changed anytime from the App’s Admin Page. Just navigate to your JSM project’s “Manage Apps” page and choose the Customer Satisfaction Survey Admin menu item on the left:
From there, you can:
Disable (or re-enable) the Display of all the pieces of info on the portal
Change the description text of the info items
Choose which of the individual elements you would like to be visible
Once you change any text strings or check any of the boxes or toggle, clicking the Save button will show the updated text in the portal, hiding the items you do not want visible.