I tried PAYING CREDIT CARD using another credit card “credit card UPI” and it works.
credit card to credit card payment is possible here -
https://customer.sbiunipay.sbi/CustomerPortal/quickPay
use this if you want to put credit on credit… ((very very dangerous… but still for the danger enthusiasts))
use SBI Uni pay and use credit card rupay upi id to pay ANOTHER credit card here THEN ONLY IT WORKS !
Credit: DEEPANGEORGE