I am making an app for my beauty salon, which will eventually replace the conventional loyalty card. I plan to implement a reward points system. Every service or treatment will carry points. When a customer collects enough points, they can redeem the points for free services.
Besides writing receipt note or invoice, my cashier will also update the transaction to the customer's account via the app. The app would then send a notification to the customer's mobile phone, and they would collect the points when they accept it.
I would face a problem with this approach because I still have random guests come in and get the treatments or services. The cashier could game the system by creating false names and giving the points to their friends or family.
How can I prevent such gaming?