Create a account on razorpay complete you KYC once your account is activated.
Navigate to offer from razorpay dashboard from there you have an option to give offer on specific payment methods like UPI 10% off DEBIT/Credit Card 20% off ect.
Hi there is a way out of ur using Razorpay. We are using the same method on our store www.trendily.in
You can create a discount coupon at Razorpay for UPI as most of the prepaid payments come through UPI, give 10% Flat Discount and mention on your store creating a new shipping method to infor customers
By this customers can go to Razorpay and opt for this payment method and will get 10% flat discount