I need advice please?
You'll have to wait it out. The guy who spread the rumor will eventually admit he lied, or get caught lying about another girl, and people will turn on him.
If they were truly your friends they would believe you and not the rumors. They sound immature, but that is expected of high school kids. If they don't believe you, all you can do is move on and ignore them. Make friends who are actually worth your time, not snobs who thrive on gossip.
They're not very good friends, if they'd believe some nasty rumour! Is there a kind adult at your church you could speak to? Preferably one who has some contact with at least one of your so-called friends? If you could explain the problem to that person, and suggest that they casually mention to just that one friend that spreading hate and bullying is such a problem nowadays, and he or she finds it sad that young people, who consider themselves Christians, are so quick to believe stupid or nasty rumours about someone they know well. They wouldn't have to mention your name - but all it takes is for a little seed of doubt to get into one of the group's minds, and that could really swing things around. If that doesn't work, maybe it's time to find another church to attend where there are good people rather than these nasty bullies? Good luck!
I'd ask them who spread those rumors, and then confront him and tell him he's gonna tell the truth. Then I'd find a new friend group outside of that church at start hanging out with them instead.