How can I address false rumors and workplace harassment legally?

I am facing serious issues at my workplace. A female colleague, who previously referred to me as "brother," began spreading false rumors about me after I sent her some formal WhatsApp messages in March 2024. These rumours have since circulated throughout the city and my village, leading to my colleagues turning against me and the department treating me as a suspect without cause. I am being harassed and threatened by my colleagues to accept unethical demands on behalf of this individual, which is defaming my character. Additionally, they are threatening to file a false case against me. As a member of the ST community, I am deeply concerned about these actions. Please assist me what can I do?