hey guys, I'm new here. I have a question: I was wondering at work how do some e-wallet offer cashback on every transaction made using them and avoiding users making back and forth peer to peer transactions? For example, Mr. A pays Mr. B 100$ and gets cashback on it. Then later Mr. B pays Mr. A back the 100$ and gets cashback too. So both users got cash back without really paying any money. Is there a way to avoid transactions like this?