Im being made fun of over something that isn't true, what should I do?

Last year i had a really good “Girl” friend. Well the relationship suddenly evolved to something so much more than i wanted it to be. So now, this year, people in high school are making fun of me calling me a lesbian and bi, and I am none of those things. I do not talk to that girl anymore. I really cannot stand her because of all this. Is there anyway I can stop it?