Lol, just when I thought I understood it, Tweetybird's last explanation confused me again!
TB, do I understand correctly that your sail and sign account was credited $130 for the cancelled excursion and then charged $135 ($90 + $45) for the replacement excursion? And that they didn't charge the original $130 to your sail and sign account? If that is the case, then it is the same as charging you $5 more for the replacement excursion and you still owe MasterCard the $130.