None of the livebearers in the world,including the Asians and American ones,do not change sex from one to another.
In some cases the males are late bloomers,and after thinking that "it"was a female,we ended up with a "confused" boy.
This is very common among swords.Remember different from gups, in swords and platies both genders look very alike.So if a male is a late bloomer without a sword,every body thinks it just switched gender,from female to male.
It is also good mentioning than in some fish there is a gender bender.Some of the females would become males if there isnt male available in their lakes or territory.This also occurs among some African frogs(remember jurassic park?and how the dinos started having offsprings?)
Anyhow,there is no such thing as switching sex among our livebeares.