OGI NEST review for Loox ‑ Product Reviews App

Close to loving this app but I'm not receiving any support from Loox explaining how to prevent everyone from using my "single code for all customers". I understand that people receive this code once they have posted a photo review but what is to stop them from sharing it to others who haven't posted a photo review - I would really appreciate someones help on this so I can feel comfortable upgrading to the growth plan