What is the ruling on reward points for Al Rajhi prepaid credit cards, which are given as miles to be used on Saudi Airlines?

Using prepaid credit cards is permissible, even if the bank charges fees for issuing them or for withdrawals, because these fees are a remuneration for providing the service, and the client here is the lender to the bank.

It is not permissible to accept gifts or rewards from the bank if the client has deposited a balance for the credit card, because these are gifts on a loan, and every loan that draws a benefit is usury (riba). This is unless the gift was customary before the loan, or it was a reward for an outstanding debt, or it was a general promotional gift not exclusive to current account holders.