Regarding ribbis, if a store charges different prices if the customer pays cash or credit card (the credit card is charged a 2.75 percentage “convenience charge”) and then the customer pays by credit card, and earns credit card points from this transaction. Is anything about this transaction violating the laws of ribbis ?
The store is charged a small percentage for the transaction, and this is being passed on to the customer. This is not ribbis because the extra charge is not because you are paying later, rather to cover the charge, and therefore permitted. If the store is charging (significantly) more than what the credit card company is charging them, then there would be a need for a heter iska. Earning the credit card points is not an issue related to ribbis.
Bris Pinchos 17-31.