mentally torture

hello sir, before 8 months , I met with a boy who is boyfriend of my friends sister. I met him as a brother and told him not to waste their time and advised him for good future. he was very happy with me at that time. but now when their is problem with their relationship he make false statement (he said that I told him that her girlfriend was not good , characterless etc etc). now they both torture me by saying wrong statement false statement, I am a respectable person in society and they know that so they threaten me indirectly. what can I do? they only do one thing only false statement about me. is police can help me in this matter because its not big crime. but I am in tension from last three months. many time people come to me and say that one girl said this about you, I know how shameful is that condition for me. what can I do. many time I said her," do as you want but don't take my name". but any time there is problem in their personal life they give me headache. They directly blame me. what can I do?