Royal Caribbean Cruises review: Reimbursement request

We were on the Ovation of the Seas cruise departed on 4/30/24 from Hawaii to Vancouver. The ship was delayed for more than 8 hours so we had to change our return flight. The original flight was booked with reward points on UA three (3) months in advance and was on sale, discounted from 15,000 miles to 9,900 miles. When we tried to rebook to flight back 2 days in advance, there were no reward seats available. We ended up in purchase new tickets in the amount of $423.86 for both of us. We submitted the receipts for reimbursement of the changed fare and RCL denied the claim with reason that we had already received the miles and the tax refund from UA. This is correct, however they refused to take into consideration of the change in fare between the 3 months advance purchase with sales price. If we book the ticket from Vancouver to Los Angeles for traveling 3 months from today it would be 17,500 miles or $117.00 in comparing to 2-day advance of $298.00. There was definitely a higher fare for the newly purchased tickets and that's all what we are requesting and after 3 telephone conversations, the representatives assured us that they are the highest authority of the corporation, and we can NOT elevate the issue any higher. At last, they referred us their legal department and we can only communicate via regular mail. Please help.