but I paid for it during the St. Pete Sail
show when we bought our 6-Pack classes. Despite the provider
having said that the Master's class would be given shortly after
the 6-Pack training, and that they had many Master's applicants
in our 6-Pack training class alone, in addition to those in the
many other 6-Pack training classes they held in the area, they
never scheduled a Master's class.

So they said they'd provide classes and then failed to do so. Seems like
you should call the credit card company and contest the transaction. After
all, they've failed to deliver as promised. This is one reason why charging
stuff like this is a good idea.