Booked a a "sightseeing tour" of Lake Mead at abou...

Booked a a "sightseeing tour" of Lake Mead at about 7PM. My wife unexpectedly woke up ill the next morning and I called to cancel as soon as their business office opened at 8am. Ginny gave me static about I cannot cancel tour unless greater than 24hrs. It was only about 11 hours since I had booked so why she would not cancel? Needless to say I have disputed the 78.00 with AMex and will not pay it.