Circle Line Cruise - Rockin River Cruise NYC Question?

I bought tickets to ride the Circle Line Cruise (Rockin River Cruise) and watch a band preform on the boat. Due to a family medical emergency I could not go the night of the cruise. Is there any way I can exchange the tickets for another night? the same band is playing next month and tickets are still available. Can I go next month even though I paid for the cruise for tonight?