It makes me sooo angry that sellers think because it's happened to them it's just how it is. Grrr
If you are going to sell something as male or female thats what it has to be.
Sellers should make sure they know what sex the snake is before selling it as one or the other, this means getting it sexed by a number of people instead of going by what it was purchased as or what it was when it was a hatchling.
I brought a supposed female snake this year that wasn't female at all, (i think the seller knew this) i made a fuss of it to the seller but because it was an interstate buy i was stuck.
But same story as yours with the seller saying "it's happened to me many times bla bla bla'
I'm now more careful with buying snakes that I need a paticular sex, I will only buy them on the garantee that if i get them sexed and they are not what i want that i can return them and get a refund, people that are sure of the sex of their snakes are fine with this but it does limit me from buying interstate.
Now if i was to buy interstate i'd probably only buy a proven breeding pair and if a proven breeding pair turned out to be wrong ohhh i wouldn't want to be that seller.