Underwear that "jumps"

I order medium size and it’s running small and i asked them to return it and get bigger size because theu have the problem there medium run small they said no we can’t because this what u ordered and they give me options that i can keep it and purchase new one with 30% of I never heard thst before

It was just underwear no device! An they was too small for my girl! Threw them away

It was jus a pair of thongs nothing else was in there