Steps
Sign up on pockets app and do kyc (necessary, maybe you will have to do offline kyc as in my case).
After your kyc is successful, you will be able to use pockets own upi.
Now add balance to your pockets card via debit card (every debit card working).
Now, pay credit card bill using Amazon (other upi apps payment option) by entering your pockets upi id.
Approve the request via notification or in-app.
Hurray! You have paid your credit card bill using debit and card and got reward points.
Also if there is an offer on Amazon for credit card bill payment, you can avail it too besides reward points.
This way is 100% legal. If you face any problem while loading balance, like limit reached, change daily transaction limit (whic is 1000 by default to 9999 max).