I get 50rs and that is the maximum amount you can get. I would advise you to set up an auto-pay mandate on the Bill Pay section in your netbanking. There, you get assured 5% cashback on the bill amount. So if you're billing is 1500 (for example), then you get 75 which is more than what you can get on Payzapp.
Also, keep in mind that you have to bear 2.5% fees + 18% GST on the fee amount to transfer the cashback funds to a bank account of your choice.
SmartBuy is a purchase portal for gift cards, travel bookings etc.
PayZapp is an open app that you can use to pay biils and also manage your smartbuy purchases.